Floating window backround color
Hi, Iooked through the documentation and browsed the source code, but didn't find how to change the backround color of the floating windows in agenda and capture modes. I'd like it to be the same color as the normal backround.

Other floating windows such as fzf have the correct backround color. I tested this with default colorscheme also, but the problem persist there. Thanks!
How is the background on the floating windows for signature help, diagnostics, etc?
We are not overriding any colors for this window (or any other floating window), so whatever is set to your NormalFloat highlight color should be used.
If you don't want to override it everywhere, but only for the org buffer, you can add something like this to your init.lua:
vim.api.nvim_create_autocmd('FileType', {
pattern = 'org',
command = 'set winhl=NormalFloat:Normal'
})
Note that I haven't tested the code above, but it should work. You can read more about it on :help winhl.
Edit: Just to correct myself, since I gave misinformation. We do fallback to normal background for calendar, help and notification popup.
That fixed it! Thanks for pointing me in the right way. Help windows and calendar worked as expected using my previous settings, which is weird.

Yeah, because those automatically do what I wrote above. I edited my initial comment with that notice.