I am fairly certain that the yellow is the hardener. My tubes are not labeled; but I know the yellow is the hardner in Flexcoat epoxy.
I coated about 20 spinnerbaits a few weeks ago and one of the 20 was still tacky after about a week. The others were fine. Very weird. Anyway, I just mixed the Devcon equally and applied another top coat. When that coat dried, everything was fine.
I have since switched over to Enviro-Tex Light, and I am much happier. The Devcon 2T was turning yellow in some batches, which would ruin a whole run of baits. The ETex takes longer to cure, but I have yet to have any problems with it. Not tacky and not yellow.
Good luck.