Anyone with a good DVD collection will most likely have a free set of calibration tests for video and sound. Movies which include the THX Optimizer
can be used to set up the colour on most TVs and to check the sound adjustments and wiring. Even though you may think
you have wired up your speakers properly, I do know of people who found out their speakers were assembled incorrectly at the factory and one or more speaker was out of phase. Some LCD TVs are a problem because they don't allow some colour adjustments when using component inputs. Some colour tests require red/blue "glasses".
THX has a list of 652 movies
which include the THX Optimizer.
Sure there are other, even better, tests, but the Optimizer is free and will get you going today. Using these tests turned and older CRT TV into a real trooper with a very nice image, but you may have to play around a bit with brightness/contrast levels for GT4. I found the tests made it look pretty dark, even though the game is dark to begin with.