Aquarium gravel comes in every color – black, hot pink, orange, yellow and fluorescent blue. The good part about this gravel is that most of it is plastic coated and therefore inert, and won't add dust or chemicals to your tank. It is also the right size so as not to get sucked into undergravel filters. The bad part is that there's nothing natural about it. A bright-colored gravel will also detract from the colors of your fish.
For more information, please read Selecting Gravel For Your Freshwater Aquarium