I've also played with the Heirloom paint (Rustoleum), and it works well if you can find a decent match.
The Evinrude polychromatic blue is a tough. I got a nice single stage match some years ago at an auto body shop, and plan to use that ppg code if I do additonal '57s. (This assumes I can find it after a couple of intervening moves.)
A few years ago (actually 8-10, I think), AOMCI collected info. on paint matches members were using -- probably still available somewhere on the site. There's a subjective element involved, obviously.
If a can or two of the NOS oem color turns up, of course, buy up what you can get your hands on.