Carbon fiber crank arm with scratches--how much damage is a concern?
The thing with CF components is that you can't really tell much about structural integrity without specialized tools and knowledge unless it's obvious from the first glance.

Anyway, SRAM carbon fiber cranks have a healthy dose of paint and clearcoat, any damage to those aren't structural. Source: I own a set of S2200 that survived a bunch of pedal strikes, coming out deeply scratched in pedal insert area. The coating has been sanded away for a cleaner look and the crankset in question has been performing just fine over years. Take this with a grain of salt, I'm just a guy from the Internet.

If your crankset does not exhibit signs of loose pedal insert, I'd just ride it and check from time to time. If it's loose, a repair is still possible, but the price might be more than a replacement Red.

To protect from scratches in the future you can use silicon crank arm boots.