I think the smell is subjective. Some people may not like it, but others like myself don't mind it. It's just new neoprene smell, not any different than new car smell. It'll go away eventually.
I think the beauty of the Neoprene seat cover material that Wet Okole uses is that it's much easier to clean than the conventional fabric material used in cars, or even leather. That's because the Neoprene's backing material is 100% water proof, so it allows you to really thoroughly wet the Neoprene so you can perform like an in-place washing almost. Along with the wet suit shampoo cleaning solution, you put a couple of drops of this shampoo into a bucket of water and basically give your cover a thorough shampoo, then rinse it with fresh water and towel try.
The darker color may hide the stains and dirt better, but that also means that you let the covers go dirty for much longer before cleaning them, which is not necessarily a good thing in terms of maintaining the cleanliness so that it'll last longer.