Can I set the rich text editor background, similar to theme-input-bg?

I'm testing the ability to change the styling on the admin dashboard and so I followed the documentation here :

I've created admin.scss with

:root {
 --theme-bg: #F7D6E0;
 --theme-input-bg: #EFF7F6;
}

This works and sets the dashboard colour and the text input field colour. However the rich text editor shows up with its background colour equal to the theme-bg (like its transparent) and I'd like it to the the same as the theme-input-bg. I assume this might be Slate related but I can't see an obvious way to configure it?

(I can set the background manually on the <div class"rich-test__wrapper"> element and it works)