Sweat will eat it away a bit especially on the stock since you hold your cheek to it But on the receiver this should not be a problem. Again it comes down to surface preparation, the cleaner the part the, the better the paint will bond, the better it will hold up. It is just paint after all, not a parkerized finish.
I think the color selection is good. Black, Brown, Tan, and OD green. What other colors do you need for airsoft?
Travis R. (aka Trapper)
Canadian Airsoft Marines. Field owner