I had a similar issue with my screen discoloring and the guys at the repair depot could not see the problem and shipped it back. Below is what I sent to Apple. This is still a pending issue. I know this doesn't really help you out, but i thought I would share.
Email #1
I got an email asking to contact Apple Care because they needed more information on my Powerbook that is being looked at. Apparently they were not able to see what the problem was. I thought I would send this as well in case it helped describe the issues I am having. The screen has a green and sometimes pink hue in the upper left corner (about the size of a baseball) when using any other color calibrated profile other than the standard default Color LCD profile. The color gets worse when I try to use a color calibrated profile, which I MUST do since the machine is used for photo retouch and photosimulations for my business. This has started happening in the past month or so and is getting worse. I brought it in to the Apple store where the Mac Genius looked at it and right off the bat said "This needs to go in for repairs". He also noticed that in the same location of the screen by the menu bar there is some distortion and explained to me that there have been some issues like this one with the Hi-Res Powerbooks. I really need to get this taken care of, so please let me know if you need any further information from me that will assist you.
Email #2
My concern was that I gave a detailed scenario on what the issue is and even called Apple Care explaining exactly step by step and what color profiles to use so the technicians can see exactly what my Powerbbook is doing. Once I gave the information, the technician sent the information to the repair depot and not more than an hour later I saw that the status of my repair said the repair WAS MADE and the powerbook was being shipped back to me. I received the powerbook and noticed on the work order that it states that the problem, could not be re-produced so they didn't do anything and shipped it back to me. The problem with the color of the screen is still clearly there and is an issue with my line of work. I spend $2500 on a top of the line laptop that I have had for less than a year and the issue that I am having isnt taken care of when I send it in for repair. My warranty is about to expire and I was going to purchase the extended Apple Care warranty, but why would I spend $350 on an extended warranty when the warranty that came with the Powerbook when I bought the machine clearly should of covered this issue, which shouldn't be happening to begin with on such a new machine.
15-Inch Powerbook G4, 1.67Ghz, 2GB RAM Mac OS X (10.4.8)
15-Inch Powerbook G4, 1.67Ghz, 2GB RAM Mac OS X (10.4.8)