I wouldn't use spray paint...first concern is toxicity, but secondly, I think it will chip off easily & look really ugly.

I've been watching the new show on Animal Planet called "Scaled" and in the episodes so far they show custom modifications using some sort of stuff in
cages (I think it's a spray-on foam that dries firm, if I remember right?) that you might look into. It would look more natural & have texture too. You might
contact their business to see if they'll say exactly what they're using? At least that's what I'd do...if you watch the episodes, you'll see what I'm referring to.

I've kept snakes for many years, I'm still using a number of hides that are either gray or light tan color...I think they came from Neodesha plastics but they no
longer make them...they also have a texture that makes them look more like rocks. They're a hard plastic with no detectable odor, I've used them for decades
with no complaints, but sadly they don't seem to be available anywhere. It's a shame, they're great, extremely durable & came in different sizes.