When painting, most people paint the INSIDE, which is why they like the clear ones. It “seals” in the paint job, making it, for all practical purposes, indestructable. You can paint on any color. Where and how will determine your final results.
Turning on a lath? I’ve seen FHZ’s reshaped. I think usually they just smooth down the response area to flat, then cut a response recess and maybe an optional schmoove ring, which is I think how mine was done. You’re not removing that much plastic. You can also adjust the gap with spacers and a Terrapin X A+ Beefcake Kit for FHZ.