On my campus, tree painting (or doing anything to a tree) was a no-no for anyone. You couldn't paint them, climb on them, nothing. So instead the admin gave greeks trash cans to paint with their org's colors. Yes, I said trash cans.
Those that didn't have a trash can had "plots" instead (rock-esque monuments in various forms). Here is the Alpha's plot:
The Kappas had one too btw but I can't find a pic.