There have been a few issues and discussions of what is referred to as the 'pink screen' or display whose symptoms had been traced to hardware component failure in them. Some third-party repair companies may still be able to get parts and a few trained specialists may be able to fix the issues of the older computers.
The PowerBook G4 series goes way back a ways and in running condition could use OS X 10.5.8 and perhaps a few third-party unix based variant systems built for use on Mac hardware. You may be able to find out more by doing a 'identify by serial number' web site search to know exactly the model you have. Also the site http://everymac.com has most machines listed and cross-references them several ways.
About that pink screen thing...
⢠pink screen Mac G4 - google search results:
https://www.google.com/#q=pink+screen+Mac+G4
⢠pink screen PowerBook G4 - results:
https://www.google.com/#q=pink+screen+powerbook+G4
Several components are behind the function of a display, be that in a desktop computer or a portable. So the defect could be a similiar part or component starting to fail. You may be able to cross reference information from sites such as http://ifixit.com to see what other persons did to fix it, or how to attempt a DIY repair.
There are two noted PowerBook G4 models, a 'titanium'
and an 'aluminum' among other build models here:
http://www.ifixit.com/Device/PowerBook
⢠identify your Mac - lookup by serial number or model number:
http://www.powerbookmedic.com/identify-mac-serial.php
for a download application database for various models see
⢠MacTracker: http://mactracker.ca
There are cables that flex when the lid is moved, and other parts that sometimes fail due to wear, age, heat, or other cause. The desktop computers that may share some similiar technologies get this issue, too. IF you can find the correct port adapter to try a VGA screen or other supported display, that may let you know more about what parts may have failed. There are several display adapters - that look similiar - & not all will work.
Hopefully this helps somewhat.
Good luck & happy computing! đ