GeForce 8600M GT (MacBook Pro) does not render colors properly

FYI: I created three balls to demonstrate color mixing..one each of red, green, and blue. To my dismay I could not get the colors to mix properly. I determined that only two colors were being displayed at a time. It took me a while to figure out that this was only happening on my computer: 2.2 GHz MacBook Pro with GeForce 8600M GT. I double checked by logging in from a second MacBook Pro with the same graphics card. I logged in with a slightly newer MacBook with the integrated graphics and the problem was gone. Is this a bug I should report?