I'm not sure of your level of experience with computers, so please don't be offended if this post seems too 'simple'.
Possibly DeGaussing your monitor would help (usually accomplished by pressing the Menu button on the monitor, finding a sub menu that's something like 'special' and activating the 'DeGausse' option). Be prepared for your monitor to seem like it's breaking if you've never done it before (it's not, trust me. Just don't do it too often simply to watch the pretty effect :P)
Then there are various other settings that you could play around with. If things start to go awry, just use the 'reset to factory settings' option and start again