Adjust background colors of medium/dark and hard/dark

[sainnhe]

Description

After using this color scheme for a period of time, I found some issues in the color palette.

1. Three background variants (soft, medium, hard) are not distinguishable enough. The initial idea is to learn from the design of gruvbox, but I was too conservative when I was designing the color palette, the distinction between these colors is not obvious.
2. The background colors don't look good on MacBook, the medium/dark background looks somewhat bright and the overall contrast is too low.

In this PR I'm trying to make the background colors of the medium/dark and hard/dark variants darker, and make them more distinguishable between each other.

I may try to adjust the light variants in a separate PR.

[sainnhe]

@antoineco @jef Could you test the medium/dark and the hard/dark variants on your machine?

[sainnhe]

Variant	Preview
Soft
Medium
Hard

[antoineco]

I think that looks alright, slightly more contrast. I'm a Macbook user and I wasn't bothered by the original palette though.
Probably what you observe is cause by True Tone, which is not directly related to the Everforest palette and apply to pretty much any program/color scheme:

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Here is an animated comparison of the changes for the medium/dark variant:

[sainnhe]

I think it's not the problem of true tone, the display difers.

Left is M1 MacBook Air and right is surface book 2, both use medium/dark variant.

[antoineco]

In the picture you shared the MacBook seems to actually have a darker background to me, with a deeper contrast, whereas the Surface looks blue-ish.

Anyway, I don't have a strong opinion on this because every time I use a different display the colors are slightly different for any given program I use. I think it's easy to get biased by using a device much more often than another.

[sainnhe]

Actually I feel that surface book has higher contrast. This color scheme looks foggy in MacBook and I think a darker background might look better.

This color scheme is originally designed in surface book so everything looks OK on it, but when using it on MacBook I always feel that something goes wrong, so I think the palette may need to be adjusted.

Another reason is that I want the three variants more distinguishable, so I want the medium and hard variants to be darker.

[antoineco]

Works for me, I like the new background palette!

[talwat]

Wouldn't this require a lot of work to update all of the plugins for various applications? And if everforest is going through a palette change, maybe just making a separate color scheme entirely like everforest 2.0 would be a better idea considering it's technically going to be a different colorscheme.

[sainnhe]

Wouldn't this require a lot of work to update all of the plugins for various applications?

Yeah, that's a problem, I'll email the plugin authors, hope they can follow the changes.

And if everforest is going through a palette change, maybe just making a separate color scheme entirely like everforest 2.0 would be a better idea considering it's technically going to be a different colorscheme.

I'd like to consider this as an enhancement or a fix, which should happen on current color scheme. I don't think it's necessary to create a separate color scheme.

Btw, the changes are small, it's OK to continue to use the original palette.

[talwat]

While I do agree, I still think the change should only be made when all of the plugin authors have been able to update their plugins.