Twenty Twenty-One: Preview Changes Background Colour To Default

[mrfoxtalbot]

When using Twenty Twenty-One (have only tested on this theme), if you select a different background colour for the site in Customizer > Colors & Backgrounds the page is the correct colour in normal view preview but reverts to the default colour when previewed in Tablet or Mobile views.

Steps to reproduce:

• Change to Twenty Twenty-One theme
• Go to Appearance > Colors & Backgrounds
• Edit background colour to anything of your choosing
• Open the editor for a page
• Click Preview
• Choose Tablet or Mobile

What I expected to happen:

I expected to see the site in the same colour as I have just chosen in the customizer

What actually happened:

Site shows with default background (#D1E4DD) regardless of what colour has been chosen

[mrfoxtalbot]

Twenty Twenty-One Preview Changes Background Colour To Default

[mrfoxtalbot]

This was reported originally here ​https://github.com/Automattic/themes/issues/4945

[poena]

I have not been able to reproduce this on other themes (though most of the themes I tested did not change the background color of the editor at all.

It is possibly due to how the background color is handled to work with the dark mode.