If you truly want a hammered look to the finish, there is Hammertite paint. You can find it at most hardware stores, etc. It's tough, & durable, & in the original version, it lives up to it's name, in that it dries to a hammered looking finish. Home - Hammerite
And while they, as well as most other paint makers have color charts
, why not just pop off the air filter housing & take It with you to assist with matching up colors?
Or... buy a fancy, light spectroscopy meter, to measure the exact frequency of the light on the paint's surface, and... once your wallet heals from it's purchase
, snag a can of Krylon.
BTW, I can't say as to whether or not Hammertite makes heat resistant formulations or not. Though it's worth checking prior to buying
it. Ditto on any other non-engine formulated paint.
Also, on auto body paint, as mentioned by another poster here, you can just buy the door ding, touch up sizes. They're smaller & cheaper than the other quantity mentioned. Not much bigger than a jar of fingernail polish.
BTW, ain't we overthinking this? Doesn't Yanmar have a basic, standard, gray color... and touchup kits of their own (albeit likely at "proprietary prices").