I prefer to have a plain white background color on my Windows work machines (mostly since it helps when taking screenshots). Selecting a plain white color has become harder over the years, as Windows has pushed for livelier background themes. There used to be a palette to choose from that included white, but that has also disappeared in the latest versions. And it seems to me that even if you selected white as a custom color previously, the Windows settings forgets it. Or does it?
The standard selector for a solid color in Windows 11 looks like this (at least right now, as Microsoft seems to like to change things regularly):

The default set of colors has the black square as the last available color. If you click on the button called “View colors” you can add a custom color. For some reason, only one. Selecting white in the resulting dialog requires a bit of clicking, as you have to force the color to black-or-white, and then pull from all-black to all-white.

Once that is done, you have white!

And when selected, the white color has a nice black outline that makes it easy to see. Select another color though, and you get the result in the first screenshot in this blog post. Where white is missing?
If you look very closely, there is a white box there. It is just barely different from the light-colored background of the dialog box (looking at it in an editor, the background color is #FDFBF8, just a little bit darker than #FFFFFF).

Before I took this very close look, I honestly thought the white color had disappeared. And went to the custom color flow each time I needed it back.
The problem is that the dialog box has gone too far in the direction of style and looking good. Over plain old function. Go back a decade or so, and this kind of selector would have a black box around each color. Just to make sure you know the boxes are there. Sure, not as “elegant”. But a whole lot more usable.
I think modern GUI design tends to go too far in the style direction, making some functionality harder to use. It is critical that user interface design works for difficult or unusual cases, even if it does not look as good at a first glance.
Grumpy old man signing off.