I am pretty bummed to hear about this.
The only other time I saw spray paint in the mtns was at the base of the Fisher Chimneys on Shuksan. Though the spraypainted arrow turned us around and helped get us back en route in the darkness of the early morning, it really bothered me. I thought about it most of the day and wondered who would have the audacity to desecrate such a sacred mtn.
What's done is done, time will wash away this travesty (I hope!).
Folks, don't ever spraypaint in the hills, be minimal with your cairning, and only flag if it is absolutely necessary (never felt the need to do this, but I have followed some crucially flagged trails..). If you have a fire in the hills (where its allowed) keep it small, do it on top of a flat rock and flip the rock over when done, camp on hard surfaces or use what's already there, boulderers: scrub off your tick marks(!!!), take the time to avoid shortcuts on switchbacks and trails, if you comfortize a bivy uncomfortize it when your done, leave no trace my friends, these hills are precious, treat them as such.