The new colorblind scheme is inaccessible for people with tritanopia #6385
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Hi @MilesBHuff! Thank you for the detailed feedback and I apologize for the delay in getting back to you. We have been listening to all the feedback closely since the beta launch of our colorblind themes. We have quite a few people at GitHub who are colorblind and helped us develop the color variables pre-beta launch, but as colorblindness affects people so differently we definitely went into the beta knowing we still had a lot to learn and improve. We are currently working on a new iteration of the themes that is exploring the following improvements across GitHub:
We will continue to improve these new themes and look forward to additional feedback from the community so we can make them as inclusive as possible! |
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Hey Miles, this is a great trick! Just curious, do you consider Coblis to be a decent colorblindness simulator? If not, what would you recommend? |
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Hi @VulumeCode Yes, this is why lately I prefer the term "color insensitive" as opposed to color blind, and I try to use that most of my writing, using colorblind only to describe those with achromatopsia or blue cone mono. Welcome to hear your opinions regarding descriptive terminology. The Myndex CVD simulator does simulate deuteranopia, protanopia, tritanopia, and not the anomalous levels for a couple reasons. First, it's based on the Brettel model, which is the most well researched in terms of matching clinically to actual perception for the -opia types. Other models seem to be comparing themselves to Brettel et alia. Though we are looking at other models to potentially adapt. But the second reason is in researching for accessibility, looking for the "maximum" cases to find fail points, and currently the primary focus is readability. The midrange cases, the anomalous types, are a part of live studies and live research that we're also conducting. Please let me know if you have any interest in that and/or commenting on anything that we're working on.
The Myndex sim does not use orange for deutan/protan—so I should ask, does the Myndex Sim appear orange to you? Being based on the Brettle models, the deutan/protan are shown blue/yellow, this is based in part on the functioning of the opponent color process of human vision, but also including studies with unilateral color insensitivity, where somebody is color insensitive in one eye but not the other, allowing them to give feedback in terms of the accuracy of colors chosen. So again this is related to the -opia not -anomalous types.
I'm not quite sure what do you mean? Tritanopia is missing the S cone, which is the blue/violet related cone. That does not mean they don't see blue. Here is a chart of normalized cone functions: Notice that the cone responses for L, M, & S all overlap very substantially. L & M cones both actually peak in green, the L cones peak in a yellowish green, but extends far into red, M cones peak in a more teal green. S cones peak toward violet.
Something we are working on are best ways to shift a color palette for Daltonization to accommodate various levels of color insensitivities. One of the issues with Computer monitors, is that they only display three colors, red, green, and blue. Yellow on a computer monitor for instance is not yellow, it's still just red and green at the same time, very close together. It doesn't mix in the air like paint or something it mixes in your neurology. There are implications here for how color insensitive vision responds to independent primaries as they exist on different kinds of monitors, an area of continuing research. |
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Hi Miles @MilesBHuff
The short answer: it is essentially the same as with other aspects of vision—you want a vision model that is close to perceptually uniform, or at least within the range you need is relative to actual perception. When modeling aspects of color (hue/chroma) you typically want to have your model doing the "Work" in (or close to) LMS cone space, in other words using reference cone data from empirical studies. DaltonLens has a good review of simulators, and I agree with his conclusions. We found pretty much the same from our research a few years ago building the Myndex color vision deficiency sim. mainly that Coblis and HCIRN & the other related sims were very inaccurate. We built ours because we needed an accurate sim to support our research into accessible readability for web content. Next post will have a brief encapsulation of important CVD considerations, stay tuned... |
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I'd like to comment on some of the thoughts that were brought up regarding accommodating user needs for those with CVD. I'm hoping this is the appropriate thread. There's additional background in each of the "spoilers", which are used to hide the bulk of the writing to make the post easier to read over all. The discussion below refers to the web standard color space sRGB, the narrowest standard color space, that requires the least heroic accommodation. Color Vision Deficiency and Colorblind Fast Facts
CLICK TO EXPAND CVD FACTS### Population and rarity As far as most common congenital (genetic) color insensitivities, deutan and protan (green or red insensitive respectively) affect 1 out of 12 men of European ancestry, but those numbers change very rapidly with different genetic backgrounds. Most reasonable estimate I've seen place the International population for all deutan and protan CVD types combined at about 5%, so a very common condition at 1 out of 20 people overall.The common deutan / protan CVD types have equivalent or better visual function as standard vision including equivalent or better luminance contrast sensitivity. Deutan have an enhanced ability to recognize camouflage compared to standard vision. The only significant functional luminance deficit is with the protan, in the case of red against black because they see red darker. Tritan: a rare CVD with anomalous or missing S cones (missing blue violet), estimates are about 1 out of 50,000. However it is useful to know that even standard vision is tritanopic in the central foveal vision, because the S cones are loosely scattered only in the periphery, and make up only about 2% to 7% of the total cones in normal vision. Because triton are only missing the S cones, which offer very little in terms of functional resolution, and are not a part of luminance, triton have no deficit in terms of readability, and their only deficit is in a reduced color gamut for discerning color-coded data. The following rare cases are not CVD, they are actually colorblind.Congenital rod-only Achromatopsia: 1 out of 30k-40k. US population is believed to be a little less than 10,000 for achromatopsia acquired through genetic background. Cerebral Achromatopsia: is exceedingly rare, Bartolomeo, 2013 discussed the very few known cases totaling perhaps two dozen patients over 40 years or so. the condition is caused by Brain trauma such as a stroke. Generally they are not co-morbid with low vision or photophobia as the standard cones are present on the retina. Blue Cone Monochromatism (BCM): presenting very similarly to congenital Achromatopsia, is co-morbid with low vision and photophobia. As we know from standard vision there are no S cones in central foveal vision, S cones are not part of luminance, and S cones carry very little detail as they are at a very low resolution. Red or Green Cone Monochromatism: there is some controversy whether or not this condition actually exists, and if it does it is so extremely rare, as in one out of 1 million to 2 million, there is very little information about the condition. Nevertheless since the L M cones make up luminance, which carries all fine detail, we can assume that they don't suffer the severe low vision or photophobia of BCM, and do see things close to a black and white / grayscale image. Green Cone Mono should be expected to have a response similar to Protanopia but virtually no blue. Readability and Accommodating CVD User NeedsUser needs follows two broad categories
CLICK TO EXPAND USER NEEDSReading All vision types need very good luminance contrast because the high spatial frequency of text, especially body text, has a much lower threshold of contrast sensitivity. Color contrasts, as in hue or chroma, do not play into readability, except if they interfere with luminance contrast or cars chromatic aberration. As such, the content author need only to make sure that all sighted users have ample luminance contrast for readability, based on the importance of the use-case of the particular text. Discerning For this reason, the single most important thing to do is to ensure that there is something other than pure color communicating the information. Color, as in Hue and colorfulness, should never be the sole means of communicating information. This is important for all forms of vision, and all visual users. for instance cultural differences may result in different color interpretations, so rely on non-color dependent indicators to accommodate all visual users. Accommodating color-coding and non-text largely requires that all color-coded information is discernible and understandable without the color (hue) being present, in other words, make it a functional design in black-and-white first. sRGB Low Fidelity AdvantageThe red, green, and blue color primaries in sRGB Color space are close enough together and create a small enough gamut that even a severe form of CVD such ias protanpia will still see the color red, but about 50% darker. For UHD or rec2020, the high fidelity spectrally-pure red primary can disappear for protanopia. sRGB is a better color space for accessibility, and it is the web default standard. Accommodating readingThe content author need only to make sure that all sighted users have ample luminance contrast for readability. Accommodating differentiationAll color-coded information must be understandable without the color being present. Color as in hue is a useful tool to enhance information, but not to be the sole source of information.DISCUSSION OF THE VARIOUS GITHUB CVD COLOR PALETTESCLICK TO EXPAND DISCUSSIONI actually wanted to talk about this last year or two and unfortunately have been too busy, but I thought I would just take a break from my other work and add some discussion.Daltonization is the process of changing a color palette of an image or other content to improve the user experience for somebody with a color vision deficiency. This could be very useful on an image to give it more apparent depth, and it can be used on a user interface in some cases. But it's not always necessary, the first question to ask is what makes it necessary? If the normal color scheme has color conflicts in it where are certain meta-states can easily be confused when viewed by different forms of CVD, that would be one useful example—but it's less common than you might think. As for readability, good luminance for standard vision is also good luminance for all forms of CVD with the exception of red and black, in the case of a protan. But accessibilityred and black is bad for all forms of vision as far as readability is concerned. This then brings up the question, was there an accessibility problem related to CVD with the standard default color scheme for GitHub? Let's take a peek at the color palettes. Here are examples of the GitHub Color schemes. The left most slice for lightmode or darkmode is the normal default color scheme, and then towards the right we have some of the other color schemes, for different contrasts or for different kinds of CVD. These samples are processed by the Myndex CVD simulator, top left is standard vision then clockwise: deuteranopia, protanopia, tritanopia. Large buttonsLight mode: default, high, deu/pro, tri. DarkMode: default, high, deu/pro, tri, dim Looking at these critically, starting with the large buttons. First, for standard vision, examine the first slice on the left of either light mode or dark mode, and look at how it was processed for the three CVD types. Are there color conflicts that didn't exist for standard vision? Is there anything that became difficult to read? And then look at the slices that are processed for different contrast or CVD types. Is there any real improvement? Or do they simply look the same? DiscussionCLICK TO EXPAND DISCUSSIONIf the human vision system is going to interpret colors a certain way due to CVD, that does not mean that it's incumbent on the designer to design with those interpreted colors, it's only necessary to be aware of them to insure that there are no conflicts. I may be missing something and I don't have the whole picture, but it appears to me here that the colors for the various CVD types are mostly the colors that would be predicted or close to them, if the normal colors were seen by CVD. This in itself does not help CVD individuals—what helps CvD individuals is increasing the distance between colors. And that was done on one button, the new issue button was made blue. But why is it not blue for regular vision? Shouldn't regular vision have that distinction other than it's rectangular shape? Having said those things, the deutan/protan/tritan versions aren't necessarily worse than the normal version, except the code highlighting deutan/protan is better in the normal scheme then the deutan/protan. Remember that CVD has equivalent or better visual function (including luminance contrast) as standard vision. The only issue for CVD (other things being equal) is discrimination of hue, and then red against a very dark color in the case of the protan. The bigger concern from a UX point of you is the large variation of color for the same button across the themes. For the default scheme, "open" is green for another scheme "open" is red for another scheme it's orange... though all of the close ovals are lavender… To me this is confusion without providing a real or articulable benefit. But then I don't understand or know what the motivation was behind this, and so I may be missing something and I grant you that. But that's also why I'm starting a conversation, for a better understanding of the goals. Next, the very thin icons Thin iconsLight mode: default, tri, deu/pro. DarkMode: default, tri, deu/pro DiscussionCLICK TO EXPAND DISCUSSIONSo, the same comments from above apply here as well, not knowing why Colors were changed so substantially when they don't seem to need to be? There is nevertheless an accessibility issue here, in that all of these icons are composed of thin lines. That makes them a relatively high spatial frequency compared to the solid buttons on the other example. The thing is that both color and luminance contrast are very sensitive to spatial frequency. And in the case of color (hue) our ability to distinguish between hue or chroma is sharply curtailed as the spatial frequency goes up, meaning as lines get thinner we rapidly lose our ability to distinguish between hues. Notice also that these thin lines against the white background lose much of their colorfulness vs the ones against the black background. And finally take a look at the tritanopia processed example you'll notice that all of the colorfulness is gone from all versions of the checkmark next to the word Tony and the switch icon next to the word test at the bottom than the other schemes. Accessible or NotIn closing, while I don't see a serious problem with the color schemes, I also don't see them as being particularly useful given the context and the very limited use of color. But I am very glad to see the exploration of visual accessible issues here, and I hope you take my comments in the spirit they were intended as constructive and helpful. I want to be clear that I don't see these specific example colors as being "not accessible", however I have to admit I don't consider Github particularly accessible overall. And here's why:
Thank you for reading, Andy Andrew Somers |
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Hey guys, The reason for this, as I mentioned earlier, is that magenta is not a "real" color: it always has to be composed of equal parts red and blue. People who can see one but not the other will still see something that is different from green, because red and blue are both maximally distant from green. |
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__Hi @adlai thank you very much for commenting, it reminded me that I was going to demonstrate to @MilesBHuff why "green and magenta" is no only not the answer, it creates severe problems and is in fact very far from the answer. Human vision is far too nuanced for something as simplistic as a conjecture such as "just make it green and magenta". Green and magenta is a terrible terrible combination. There are examples of green and magenta, processed using a clinically accurate simulation of color vision deficiency. For each slide in the upper left-hand corner is standard vision and then several forms of CVD. All the slides are green and magenta, at various levels of brightness, and showing that the assertion that these are all equally readable for all vision types is quite simply not the case. #fg vs #bg#090 #f0f#0c0 #f0f#f0f #0c0#f0f #090#c0c #090#c0c #0a0#090 #c0c#0a0 #c0cThese should be enough to demonstrate that this color combination is pretty much bad for everybody all the time, but I provided some examples of when it's best for one it's also worst for another. While you can see the giant ampersand, that's only because it's huge and therefore a very low spatial frequency, the remainder of the text is pretty much unreadable. In other words, this combination doesn't even work, much less be the panacea for all people.Human vision is far too nuanced to try and say "it needs to just be this and then everything is fine" because that's simply, absolutely, not true. Thank you for reading |
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(Originally posted here: https://github.saobby.my.eu.orgmunity/t/the-new-colorblind-scheme-is-inaccessible-for-people-with-tritanopia.)
Orange/blue is not accessible for people with tritanopia. The only two-color scheme that works for people with all three types of single-cone-deficient color-blindnesses, is magenta/green. You can easily verify this with any decent colorblindness simulator.
The reason magenta/green works for all three, is that green is in the middle of the visual field, while magenta is a “fake” color (As in, there is no such thing as a “magenta” wavelength of light.) that is composed of equal parts red and blue, each which are at opposite edges of our visual spectrum. Someone with a deficient red cone (protanopia) will still see magenta as blue; someone with a deficient blue cone will still see magenta as red (tritanopia); and someone with a deficient green cone (deuteranopia) will still see the two as different hues, since green and red/blue are maximally distant.
As well, magenta/green is much easier for non-colorblind people to adjust to than orange/blue, as magenta/green is a strict superset of red/green (since magenta is by definition equal parts red and blue).
I figured this out a couple years ago by playing around with a color-blindness simulator until I found a color combination that worked for all 3 single-cone-deficient color-blindnesses. The explanation above as to why this is the case is original theory.
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