There is a possibility the graphic processor may have issues;
in some model builds iBook white G3 and G4, there were a
few solder joint problems and a re-flow or reball fixed them.
What happens if you go through the PMU reset sequence?
•Resetting PowerBook and iBook Power Management Unit (PMU)
There also is a PRAM/NVRAM reset; this page changed recently
to show Mavericks info, but the instructions should be the same:
•OS X Mavericks: Reset your computer’s PRAM
However, to see if the internal display is at fault, you could
test the graphic processor with an external display via an
adapter; if you have one or can find the correct one for this.
The display is the last link in the chain, so it may not be defective
if the backlight and liquid crystal panel both appear to be OK.
The data getting there appears to be corrupted due to some
defect, that may be more involved to troubleshoot than repair.
For a modest fee, there still are companies who do most repairs
on almost all Apple portables with rarer models an exception due
to parts and systems availability issues. wegenermedia and
maybe powerbookmedic, among others. However, for sake of
more practical usefulness, the MacBook series 2006-2010, is a
better investment if one has no need to run Legacy Mac OS apps.
The sites powerbookmedic and ifixit.com have guides to look into
the complexity of most repairs in these tightly-packed portables;
a problem with a repair, is the possibility of further damage that
results from attempting to solve the first known problem...
Good luck & happy computing! 🙂