Add info about customizing colors with Stylish to the FAQ

(closes #4270)

FAQ.md

@@ -2,10 +2,12 @@
 
 Two syllables: "eye dee".
 
+
 ## How can I help translate iD into another language or fix a mistranslation?
 
 Please see [CONTRIBUTING.md](https://github.com/openstreetmap/iD/blob/master/CONTRIBUTING.md#translating)
 
+
 ## How can I report an issue with background imagery?
 
 To report an issue with missing or cloudy imagery:
@@ -17,6 +19,19 @@ iD's list of available background imagery sources come from the [editor-layer-in
 project.  If you know of a more recent imagery source that is licensed for this use,
 please open a request there with the link and license details.
 
+
+## I'm having trouble seeing some of the colors. Is there a way to customize or change them?
+
+Because iD uses CSS and SVG for all its rendering, users can override the colors
+with the [Stylish extension](https://en.wikipedia.org/wiki/Stylish) on Firefox or Chrome.
+Stylish also allows users to share custom styles with others.
+
+You can find detailed instructions on how to install Stylish
+[here on learnosm.org](http://learnosm.org/en/hot-tips/enhance/).
+
+See also: https://github.com/openstreetmap/iD/issues/3095#issuecomment-224988925
+
+
 ## Why not use canvas rather than SVG?
 
 Using canvas rather than SVG would require implementing a scenegraph, hit-testing,
@@ -32,6 +47,7 @@ In other words, the decision to use SVG rather than canvas was a classic perform
 vs. implementation cost tradeoff with strong arguments for trading off performance to
 reduce implementation costs.
 
+
 ## Can I use iD offline?
 
 iD does not currently have an offline mode.
@@ -47,6 +63,7 @@ We've thought a little about [caching tiles](https://github.com/openstreetmap/iD
 and downloaded data, but haven't actively worked on it, nor on the data download/upload
 question.
 
+
 ## Can I use iD with my own OSM server?
 
 Yes, you can. You will need to [install](https://github.com/openstreetmap/openstreetmap-website/blob/master/INSTALL.md)