I've had this happen on K4900s over the years, albeit, they turned red. I assumed it was an electron gun short, but would you believe, it just wound up being dirty cutoff pots on the neckboard. so I encourage spraying the 2 drive pots and 3 cutoff pots with deoxit and turn the knobs back and forth several times each (this is a process called wiping; ie. wipe the pots) and then you'll have to white balance the monitor again after. with a game or pattern generator with a predominantly black screen ensure first that the brightness is set to where black is actually black, you don't want grey pixel dots, that's too high of brightness. then turn each of the red/green/blue cutoff pots up fairly high until the picture tints that color, then back off until it turns black again. your monitor will be white balanced and your original full blast green issue should go away.