I'm just guessing here, but perhaps the "regular" key is what you'd give your wife or 17yr old kid to drive with, while you keep the red key for yourself, because it would operate the car normally vs. high-performance mode. IIRC the old ZR1s came with a "valet key" that greatly limited the car so someone couldn't pull a Ferris Bueller's Day Off like the parking garage attendants did with the Ferrari. The "regular" key wouldn't limit the car's performance so much that it wasn't passable, but it would hobble the thing to prevent shenanigans.