There is the problem that the black blocks UV. As it fades, there is less UV protection, so the material will rot from sunlight much quicker if faded.
I had a set of "Bagman" cloth bags years ago that faded badly. I used simple cloth dye on them, using a strong mixture. I used a clothing marker to recolor the stitched in logo.
I hear there is spray made for car cloth seats. That might work. May not be waterproof though.
