I've seen slant six engine blocks in many colors, do they mean anything? I'm asking because I'm trying to find out what the correct block color was for a 1971 slant six 225.
Chrysler Blue is correct for a US- or Canada-market '71 Slant-6 in a passenger car, regardless of whether it's a 198 or a 225.
More detailed info on block-head paints in various years and markets here, and engine accessories and tinware here.
The Mopar Performance engine paint is of crummy quality (and the red is a poor match for the factory-applied red, at least on Slant-6s). If you're going to the trouble, pick a better brand. Bill Hirsch's stuff is probably the best on the market, but it's expensive and you'd have to get it put into spray cans. Krylon or Dupli-Color is a better-than-MP option you can pick up easily.