Video shows strange "high contrast" display upon boot
Hi! A customer returned an iBook G3/800MHZ...it booted fine, and looked great upon booting, but about 10 seconds after the desktop appeared, the video suddenly switched to an odd mode that I can only describe as looking like the contrast was cranked all the way up, or possibly switched to 16 color mode, or something similar. It did not seem that there was a defect with the screen, and it did not behave like the common G3 "video issue" that is so prevalent. Again, immediately upon boot everything looked fine, option mode looked fine, the Apple icon while booting looked fine, etc. It's just upon completion of booting that this weird mode kicked in. The video preferences did not show any altered settings, and the computer showed that it was in the highest resolution mode with full color.
The user stated that the strange mode suddenly kicked in while watching YouTube. Granted, a G3 is not going to be the best platform for YouTube viewing, but is it possible that the video chip "blew a fuse", so to speak, dealing with video that it couldn't handle?
I re-imaged the laptop, and now it's fine again, and I'm watching YouTube with no problems. I'm just curious though if anyone else has run into this bizarre issue.
Similar to what machead3 said, it could be Universal Access.
To test this on your Mac, simply press ctrl-opt-cmd-8 to turn it on and off. It should be disabled by default. This reverts colors, which makes it easier to see text (white on black is easier on the eyes than black on white).
I use this sometimes on my MacBook when viewing a white page and I need to save battery - I can have the contrast almost all the way down and the colors inverted and still see and read text fine.