Can a combat level 60 defeat green dragon by wearing rune armor in Runescape?

Yes, you can wear rune and fight green dragons. I'm guessing this question is pertaining to Elvarg more than just regular green dragons. If that's the case, you can still fight Elvarg while wearing rune, you just can't wear the rune plate as you have to defeat Elvarg in order to wear it after returning to the Hero's Guild for your reward.