Hi @MCain while painting does void the warranty, I have had customers use the proper non-metallic paint with success, but tend to go more towards vinyl wraps now to preserve the warranty. So in addition to some of the pre-made solutions, I had also had customers use a local signage shop that does vinyl graphics & wrapping. They wrapped their APs for around US $30 per AP. One was a zoo that wanted the outdoor APs and external antennas to blend in. Some where camo, some were brick pattern, some just matched the wall color. So you have options there for pre-made and also perhaps search for local sign shops or someone that does vinyl car wrapping or laptop wrapping for example. If you want to DIY, the material is fairly cheap and also looks pretty simple to do (depending on how much of a perfectionist you are!)
