Colors are not printing the acutal color
It all depends on the meaning of 'not properly'.
Try creating a document with four different squares, or words, of these colours: yellow, magenta, cyan and black. If all of them print (albeit not with the correct shades) it is probably an ICM driver error. But my guess is that only one of those four colors will print badly, due to a defective color cartridge.
The OKI 5150 makes all perceivable colours using cyan, magenta, yellow and black toners, so if one of these malfunctions, the resulting colors will lack the required shade of, say, yellow, and will appear to be "wrong". The yellow colour itself, of course, would simply disappear (the "yellow" you use might actually be 95% yellow and 5% cyan; then the "yellow" square will be printed as a very light shade of cyan, while the other colors - say, 95% magenta and 5% yellow - will turn out almost exact).
Try with the color test and replace any failing cartridge; if all four (almost) pure colours do print incorrectly, it's unlikely to be a cartridge problem, and we'll have to dig deeper.