What type of Mac is it?
What version of OS X?
ColorSync has nothing to do with the amount of color, or lack thereof, on the screen.
That is all controlled by the Graphics card. Without any model details, it is next to impossible to supply an answer to your question.
P
I have a Mac and it is black/white in OS X. The latest colorsync has been downloaded and installed. It works fine on OS 9. I have searched Google but cannot find anything like this. Does anyone have any ideas?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic