Allow users to create their own color schemes

[MirceaKitsune]

By default Mastodon comes with 3 themes under https://instance.social/settings/preferences/appearance that you can choose from: Dark, Light, and High Contrast. This is great... but why not allow users to create their own color schemes? I've found that none of these really do it for me, and would enjoy the ability to customize color sets directly, ideally also being able to import and export them using json or xml.

I'm suggesting this assuming the feature would barely put any load on servers. We can store them as hexdecimal colors, like "ff0000" for red. Out of curiosity I checked how many such colors you can write in a normal toot (under 500 characters) separated by one symbol; The answer seems to be 71! IIRC a theme doesn't customize anywhere near this number of colors, so the info would weigh less than storing the text of one single toot.

[trwnh]

Themes are currently compiled with SCSS and would require reworking to use CSS variables instead.

[downeymj]

would require reworking to use CSS variables instead

It seems that this has been done, perhaps this can be revisited?

An admin setting to adjust the SCSS color variables is urgently needed: The new "brand purple" color does not meet WCAG accessibility guidelines for link colors in the light and dark themes [0] so many users will need to find a way to change them as soon as possible.

[0] https://chaos.social/@rixx/109346884426553139

[Sominemo]

I wonder if using client-side CSS variables would be workable? This way admins will be able to redefine the color scheme easily with custom CSS. I'd like to hear maintainers opinion on this.