What is causing HVAC odor?

I have an Unico HVAC system w/ Bryant AC units that use Puron 410A. There was a leak and the contractor recharged the system. Now I have a smell like Crayola crayons coming from the system. It started this winter when running the heat and is there when just the fan is running and when the AC is on. The contractor can't find anything wrong with it. But there was a dried pinkish substance in the drain pan (no odor). 3 questions: What does Puron smell like? What does it smell like after it hits a heat exchanger? Would the Pink residue have resulted from the Puron leak? Or from an oil leak?