It actually sounds as if the green is dropping out and leaving the red and blue ("red/purple mess").
I'm going to assume that you tried adjusting the color pots before posting this question? Grant is correct that the drive transistor could be bad, as well as the pots controlling both the green drive and bias, and solder joints being faulty. You could also have a bad connection with your green signal wire on your video connector or edge connector. It could be a bent pin on the neck socket. It could be a problem with the green gun in your tube. It could be your video processing chip on your neckboard.
Since it sounds like your technical expertise may be limited in this area (and monitors are a different animal and should be treated carefully), it might be a good idea to return to your "local TV guide" and have them fix it for you.
By the way, this isn't the same MK board you blew up, is it?