The sandpaper feel of grip tape is made with various materials, depending on the company that made it. Some black grip tape companies use silicon carbide - a very hard material that stays sharp for a good long time. Other companies use aluminum oxide, which is cheaper but looses its edge and grippyness quickly. Some black grip tape and most colored grip tape are made with this cheaper material. Usually, if you want colored grip tape, the trade off is that the board won't stick to your feet as well...