Hi, Teresa. If you are really running OS X 10.0.x on a Powerbook G4, it isn't Aluminum; it's the very first Titanium Powerbook G4 model, made between January and October 2001. While the computer may still function just fine, its LCD display has aged quite a lot in those 6-7 years, and no longer is as bright, as contrasty or as consistent as it once was. Its color may also have shifted considerably toward the red, especially when it's just warming up or waking from sleep. The age of the display alone may account for most of the problems you report, and you won't be able to rectify them on such an old display. Therefore you've been well advised by the previous posters to buy a good external monitor and use that for your photo-correction chores.
And if you're really running OS X 10.0.x, you should consider upgrading to one of the more complete, mature, and stable versions of OS X and see what OS X is supposed to be like. Until version 10.2, OS X was unfinished, unready, unstable, and nearly unusable. If you've been struggling along with a beta-level operating system all these years, you're due for a more pleasant experience. I highly recommend that you upgrade to 10.3.x or better and see what you've been missing.
