Restoring Plastic Buckles

I just got a used plastic boat a few days ago. It is around 8 years old, stored outside, but out of the sun, the plastic of the hull looks great, but the outfitting needs some work. New bungees are the first thing, maybe a newer style seat, but what i am wondering about is that the buckles for the hatch covers look quite faded. They still have lots of snap and work fine, but they just look bad. Is there anything i can spray or rub onto them to make them look more black again? Would 303 work for this?

303 will make them look nice for
a while, though others may suggest a more permanent overcoating.

Sharpie Marker?
Snap-buckles are pretty cheap, so you might just replace the old faded ones. I have used broad tip black Sharpie markers to perk up or fill in scratches on dulled black items many times. You could try it on the underside of one of the buckles and see how it looks. wd

the stuff car nuts use on their tires