I'm currently painting a 1997 Quincy "Barney Edition" (that was purple from the factory) blue.
I picked up two of the closest colors I could spot at the local Home Depot... Krylon True Blue and Rustoleum Safety Blue. I thought the Safety Blue was going to be the way to go, but I shot both colors on a piece of scrap and took it to Northern Tool to hold up to the Quincy compressors they have in stock. The Safety Blue it too light/bright. It actually was a much closer match for the Puma compressors they also had in stock. The Safety Blue is also a very close match to my Miller welding table - it's just missing a tad of green (i.e., the welding table is a tad more green).
The Krylon True Blue was closer to the Quincy compressor, though perhaps a tad darker. I've got the compressor painted, but not the tank. My garage lighting is making it look much more of a dark navy blue color, but I'm going to have to trust my test at Northern Tool. I wouldn't care so much, but I plan on getting a Quincy air dryer, and I would like for them to be a decent match.