Different CSS changes for different color schemes

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@Renato_Mendes

As I’ve been able to understand so far, any change in CSS is applied to both light and dark mode, which doesn’t make much sense.

If I understand the issue well, there’s a specific thing to do for this.

Update themes and plugins to support automatic dark mode

Great question, I tried this and noticed that we didn’t properly support using background images or theme variables in the special color definitions stylesheet. So I made some fixes in core, and you should be able to do this now (make sure you pull the latest core). So, if you have two images in your theme or theme component, with SCSS vars of $bg-light and $bg-dark respectively, you can add this to your color_definitions.scss stylesheet: $bg: url(dark-light-choose($bg-light, $bg-dark)); :ro…

I’ve been working on a guide about this, but I’m struggling a bit to merge information so it’s clear enough to directly use the information in a theme, but still explains underlying technical stuff.

To explain how to do it the most clearly as I can…

I suggest you create a theme locally (using Install the Discourse Theme CLI console app to help you build themes will help).
Then, create a common/color_definitions.scss file in your theme, in which you write:

$my-color: dark-light-choose(#FC3468, #FF93AC);

:root {
  --my-color: #{$my-color};
}

Then, in common/common.scss, you can make use of the variable like this:

h1 {
  color: var(--my-color);
}

It will automatically pick the right color when in dark or light mode.