Theming is unclear to me.

[spikespaz]

When I use the theming properties on the root <html>:

<html data-color-mode="dark" data-dark-theme="dark">

And set the background color of the <body>:

  <body class="color-bg-default">

The page remains white. Why is this?

[simurai]

Hmm.. that seems correct.

How do you load Primer CSS? Maybe the color variables are not loaded? If you inspect the <html> element you should see a bunch of --color- variables like:

can you see them in your case?

Here a Codepen to test https://codepen.io/simurai/pen/BawPeqj?editors=1000

[spikespaz]

There was another class on a flex div that was unexpectedly changing the background.