Just get a little dirt and mud in the tape and rub it around, it will take the shine out in no time. If you want to take a bit more time try taking a little super fine sand paper to the surface to break up the shine of the outer layer of the nylon shine. Though usually normal field wear and tear will get rid of a nylon shine in no time.
Nice to see someone doing something on their own. You could also try to flip the tape if you want better grip on the finger that tucks into the loop for pulling the mag out of its pouch. Though with it on the outside one can easily squeeze it between two fingers and pull it out with a decent amount of grip as well.
That almost reminds me of an MP5 mag in 9mm.
Razor