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.


Thank you for telling us about this, I am learning this more and more.

I am very happy to GH adding a colorblind scheme and I look forward to them continuing to improve it.


I already missed the green buttons.


I agree, image
these two looks very similar to me :confused:
I was able to separate these two much quicker before colorblind mode.
even tho I have protanomaly


I agree with all of this… I can’t tell the difference between the different blues? purples? :man_shrugging:

Also these in the PR diffs, can’t tell the difference in the “line added” and the “shortened sections”… throws me off on how many “changes” are being made :confused:


Wow, programming is very fucked up for you.
I think every big company should know about this green magenta trick.

So far I haven’t had issues with the colorblind theme (I’m red-green colorblind, strong deutan) but there are a few types of other color vision deficiencies that will need different colorblind themes.

I suggest heading to r/colorblind to discuss it and survey the subreddit. The r/colorblind community is very helpful, just make sure to discuss with them what to ask in the survey before making the new theme because lots of surveys fail to ask proper questions since I assume it’s hard for normal color vision people to really know what works for us and what doesn’t.

I hope this was helpful information!


I was about to comment about this. I also have protanopia and these icons are messing up with my head :joy:


Thank you @MilesBHuff for your feedback and welcome to the community! This is great feedback–and so important to get more eyes on (no pun intended). Would you mind sharing your feedback with our Product team here so they can see and track? Accessibility is crucial and sometimes it takes a village to improve.


Hello and welcome to the community, @alecmce!

Welcome to the community, @Visagalis! Thank you for the feedback; please feel free to share it with our product team here.

Glad to have you here in the community, @iammarxg :smiley: Also feel free to share it in the feedback discussion with our product team!

Welcome to the community, @jeanbarriere. :smile_cat: Do feel free to share this feedback with our product team.

@tajmone Saw this thread and thought of you as you’ve done some amazing work in visual accessibility.

Ciao @tuves! and thanks for letting me know. I actually saw in the Beta features, and was really glad about the news. For people affected by color blindness is very stressful to read web pages that are not accessible, especially with dark theme and code highlighting.

Unfortunately, I can’t really benefit from viewing this Beta feature, since I’m not color blind myself. The best one can do is attempt to tell the OS to use a color blindness color-profile (there are actually different types of color blandness), but most browsers don’t support color profiles (which is why it’s important that the website provides a color blind accessible CSS file!).

When I design color palettes, I work with color tools that test for all the different color blandness, and even show me how the palette is perceived by the different color blindness (using color profiles manipulation). There are also metrics to measure the accessibility of color contrasts, and I always check the background and text colors against those metrics.

It’s really good to see that GitHub cares about accessibility. Maybe this will set a strong example and prompt the major browsers to push for the support of color profiles, which would then allow color blind users to adjust any website thanks to color profiles manipulations.

Best regards


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Done! Link is here: The new colorblind scheme is inaccessible for people with tritanopia · Discussion #6385 · github/feedback · GitHub. Thanks for letting me know about the feedback portal!

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These are very similar. I don’t think that’s because of your protanomaly.

I think this is a great idea. The switch of greens to blue is very jarring. Though it’s important with how they interact with the surrounding colors that don’t get changed, like @Visagalis points out. You can’t just swap two colors in your color palette and call it a day, because then you aren’t considering how a color blind person can differentiate those new colors from the other colors in the palette. I’d say that currently the color blind theme creates more problems than it solves, though of course that’s dependent on color blindness type, and I really appreciate any attempt to increase accessibility for color blind people. Though usually my preferred approach, sometimes used in games, is to let people simply create their own palettes so every color blind person can create something high contrast unique to their vision (I say “simply” though of course it’s not so simple).

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I found “Purple Heart” would be a good color to associate with the spirituality of the color red.
“Felwood Leaves” is a similar color in contrast. What do you think?

@kevincrans Purple Heart is a bit lacking in the red department, being a hue of 288°. Magenta is a hue of 300°, red is 360° (or 0°), and blue is 240°. A purple that captures the “spirituality” of red should be closer to the tyrian range, around 330°; however, any significant imbalance of red and blue will likely only harm accessibility.