There's no difference between "red" and "yellow" in general.
The difference is when they offer a "yellow" version for a car. That means it has firmer valving and usually is externally adjustable.
The fiero already has stiff valving and is externally adjustable in the rear. The front, even if externally adjustable, you'd need to take out to adjust so why have the additional cost?
Reds are fine. You'll be happy.