Think about automotive touch-up paint, maybe. Take a photo with your cell phone full-screen of the color, in natural lighting. Then print it out and compare it to the compressor. If it's a good match, take that to an auto parts store and look at the color sheet or book for touch-up paints they sell there. You should be able to find a pretty good match. You might have to order it, though.
It's more expensive than Rustoleum, of course, but...
Sand, shoot some gray primer on the thing, wet sand with 400-grit emery paper, and spray away, after masking however carefully you want to. Once the whole thing is painted, you won't be able to tell that it's not a perfect match.
I think there is a Rustoleum Tan colored paint. If that's close enough, you're done.