Here's a pic of one of my lenses, this is candy black.
You can pay me to do it, or you can help out on the snake and when it comes time to spray the snake we'll do it for free.
You can't use a color if you want to be able to see your lights, you need to dye an intercoat and then spray it with clear to protect the dye which will fade in the sun if you don't. The lense above was done with 5 coats of candy, then 3 coats of clear. If you don't want it so dark we can do less coats of candy. Candy comes in a bunch of different colors, but the dye is
expensive, so if you want something other than black you'll need to buy it.
To prep, 320 wet to remove oxidation then 600 or straight to 600, wet. If you're doing headlights you might want to finish with 1000, wet.
If you're set on metallic paint, I would try to do a metallic pearl intercoat and then clear over it. If you go easy on the pearl it might work. But body paint? No way.
If you try to spray 1K (rattle can) clear over spray paint, it will likely react with the paint and shrivel up. Or if you want you can use that rattle can tint, but it looks like crap IMO. I have a can of that night shade stuff laying around somewhere.