What are the panels and main enclosure coated with?

Have they been painted or have they been powder coated?

I've easily cleaned the inside residue with a product called Simple Green. There's another product called Purple Power that's even more aggressive but on other projects I've seen evidence of discoloration of painted surfaces if left on too long before rinsing.
I know I can try a small hidden spot on the interior of the panels to test but I'm wanting to paint the panels in a custom color. I don't want to put paint on only to have it chemically destroyed later.