The basic theme for Gamma Docs is not the best. You can make it look a lot better and be on brand with your logo, colors, fonts, etc. Go into the settings/themes and play around a bit until you get something that looks good.

I'd always recommend a white/light background with black/dark text, as this is the easiest to read.

Gamma Documentation:

https://help.gamma.app/en/articles/7852253-how-to-create-a-custom-gamma-theme