@MartinHatch Oh, very simple! If you go in the preferences, under appearance you can choose a "Site theme". I am not 100% sure if all servers have the same themes... but I can see a "Mastodon Default Theme, Full Width (dark)" and a light counterpart that work well with the advanced web interface. Other styles seem not to work that well for me, but that might depend on browser, resolution etc, I guess. Easiest thing is to try and find one that you like!