On a recent trip up by Denali, DEET drops took the color right out of spots on my sunblock shirt and (sigh!) my go-lite gortex jacket. Luckily, it didn't effect the integrity of the gortex. I don't usually use DEET, so this was a new experience.
From now on, I will never use DEET spray, only DEET in a roll-on. Same with sunscreen, roll-ons are so less messy.