From dalton website
Secondary Springs- Secondary clutch springs are a component that has many overlaping features . Its principal function is torque feedback sensing,that is that it initiates backshifting of the belt to proper ratio to maintain rpm. The secondary,however does have effect on upshift characteristics.CVT's are about efficiency. Proper balance of components for efficiency is the way to good belt life. The key to preventing slippage is having the belt in the correct ratio at the right time.
I think purple is a stronger spring than stock. Then I believe gold is after purple. If that makes sense lol. I could be wrong though.