My door sticker says my paint is "PDN" - Sting Gray but I have no clue where you would find matching frame paint. I would call it "thin black with green tinge" LOL Good luck!
We touch up the paint on our frames with POR 15. They sell little touchup kits with tiny cans so you're not wasting too much. Doesn't get seen, and the POR 15 will help with any rust that's developed so it doesn't bubble up and flake off down the road.