I'm not clear on what you mean by "while surfing." Are you looking to have some sort of background color in your browser window?
Firefox can do this in Preferences under Content --> Fonts & Colors --> Colors...
Most sites will override this option with their own color scheme unless you uncheck the option box in the colors preferences to "Allow site to choose their own colors, instead of my selections above."
Can't really imagine why you'd want to do this, as it really screws up the look of a lot of pages.