As someone who prefers a solid color background, I’m always surprised by how often this simple preference leads me into bizarre rabbit holes. Some additional examples beyond the OP: - In the latest macOS, trying to set a custom solid color background just gives you a blinding white screen (see: https://discussions.apple.com/thread/256029958?sortBy=rank ). - GNOME removed all UI controls for setting solid color backgr…
It kinda seems to me this is better solved by a webapp that lets you generate any background image and download and you set it up on your OS.
Just offer a background picker, and have it generate a 1x1 PNG, for the color selected. Just like that, you can use the image background code path for everything; and the code for generating the image almost certainly exists in the OS already. Maybe add some metadata to the generated image to filter it from the images picker, and you're done.