I have brain fog and my brain and eyes are very sensitive to colours. Solid colours such as solid black backgrounds hurt me, they literally give me a feeling of pain when I look at them.
I feel best when the screen or the paper I read is white and the letters are black. I also feel good when I see shades of grey or pale nuances or very light green or blue.
We are all different in terms of preferences. For me it's not a matter of preference, I love colours, but my brain can't deal with bright, solid, intense colours.