After some experiments, I can confirm that K&B Superpoxy Catalyst works just dandy with Klass-Kote color. I needed that combination for reasons I don't to go in to, but I mixed it up and sprayed some test patches, and no problem at all. If anything, it zapped off faster with (maybe 30-year-old) K&B Gloss catalyst than with the regular Klass-Kote gloss catalyst. I thinned it with Klass-kote reducer, and that also seemed to work pretty well, too. I know that Klass-kote reducer *doesn't* work with K&B Primer A/Primer Catalyst, you need Superpoxy/Ultrapoxy thinner for that. But no problem with the KlassKote A/K&B "B"/Klass-kote reducer.
I haven't tried the other way - K&B Color with Klass-Kote catalyst. Dave Platt says it works, and he is certainly qualified to say. But I haven't tried it myself. I can't really see much reason to do that unless you need to match old colors. Klass-kote has a much better selection of colors than K&B ever did. I would be interested to see if the thinner works, or you need K&B thinner.
I would also note that despite the comments instructions that you could spray it with no reducer, I can't imagine any C/L application where that would be true. It varies from color to color, but white Klass-Kote A comes out of the can with a consistency somewhere between honey and pudding. The catalyst thins it a bit, but I still needed something like 1:1:2 Color/Catalyst/Thinner to get it through my airbrush, and I needed at least 2:2:3 with a regular touch-up gun. With the same settings, K&B would need about 1:1:.9, so klass-kote is *much* thicker. It also covers much better, so I expect that the difference is the pigment quantity, but I can't see any way in the world you could ever use it without thinner. Once you do get it thinned out enough, it flows out beautifully and stays liquid long enough that you don't have to worry too much about rushing to avoid the overspray.
Brett