A complicated background makes text quite hard to read. If you are not sure, make it dimmer. Don't tinker with colors just for the heck of it. The standard choices make detecting links and such easy for users. You ought to have a reason to break that.
Some users are colorblind.
A red background and green letters looks like an empty page to them. A trick to ensure that colorblind people can read your page is to turn the monitor to black and white. If you can still read it, then so can colorblind people. Don't use totally saturated colors. That means that bright colors, such as full red, look awful, especially in combination with other ones, unless put together very carefully under just the right circumstances.