I think it is your CRT (cathode ray tube) monitor. If you're good, you can open the monitor case with power OFF first (monitor generates 15K d.c. You can die!

) and check to see if the CRT board on at the end of the electron gun is okay or not.
Only red and green is not perfectly working. If theres a chance, I could even replace that part myself. But if you're not sure what to do, don't do anything. But I'm positively sure that your monitor fails to shoot RED and GREEN color. You still have a warranty correct?