They make doors and windows out of fiberglass, and they get painted all the time, so I wouldn't anticipate any more problem painting fiberglass than any other material.
I wouldn't paint my neighbor's anything without his permission, tho.
But, if I were doing it, I'd prime with a primer that will stick to darn near anything, and both Zinsser's "Bullseye 123" Latex primer and Zinsser's "BIN" shellac based primer fall into that category. I expect both would stick to fiberglass like chewing gum to the underside of a church pew.
Then top coat with the paint of your choice.
I see the problem of how to physically apply the paint to a wavey surface like a corrugated material as being a difficult one, tho. I suppose brushing or spray painting would work the best, but I don't expect either method would be a pleasure. Rolling might work if you could find a small enough diameter roller sleeve. Your neighbor might not be upset that you painted his fiberglass, but he may take issue with the quality of the paint job. After all, everyone else will presume that's HIS skill and ability on display.