I usually just leave it on whatever the default is, so I guess light mode. I did try dark mode for a few things on my work computer, but I didn't like it so I switched back. I find it harder to see things when the background is too dark. However, if a custom option is available, I will sometimes pick a mid-range color background with lighter text. For example, I have the main system I work with for my job set to a slate blue-gray background with a combination of white, light gray, and bright blue text for different fields to make the headers and things stand out.