Did you pick the Debian Rolling Release or another one that picks Green as their
main color? There should be ways to pick your own choices if you prefer.
Depending on the Window Manager it could differ. For Firefox you can find
Preferences under the Edit Menu, on Windows it's Tools, then Options.
Right now I'm working on my PcLinuxOS LXDE computer, but typing this on my
Ubuntu 10.04 Gnome computer.