I too have seen this problem and I posted some images I took in a new thread I created before finding this thread:
http://discussions.apple.com/thread.jspa?threadID=1065874&tstart=0
At first the issue seemed to be related to installing updates that required a reboot, but that was likely just when I noticed it because those were the only times I ever rebooted. Now the problem has become more frequent and it doesn't matter why I reboot. I can reboot for any reason and about 50% of the time I get the psychedelic colors. A PRAM reset always sets things right, but It's a real pain because I use an open firmware password which I must disabled before I can reset the PRAM. I've tried leaving the open firmware password disabled, but that doesn't seem to make a difference.
FYI, I am running boot camp 1.4 and have all the latest EFI and SMC updates installed. I've also installed and since removed both VM Ware and the Parallels demos.
If anyone knows a fix for this, please let me know.