I used to recommend something that was either "Battleship Gray" or "Machinery Gray" for rowboat motors. You should be able to get it in either aerosol spray or in the can for brush application.

You can get something pretty close to the colours you want at a NAPA store. I use rust enamel on rowboat motors. The stuff I buy in Canada isn’t available in the USA. I use "Misty Gray" rust enamel. When it cures, it is very resistant to gasoline. I drip gas on it a lot and just wipe off, it suffers no damage. You can prime the base metal if you want, but for rust enamel, I never do.

Hope it helps.

Best,
PM T2