Price of diamond depends on 4C’s i.e. Color, Clarity, Cut & Carat. So, yes, the color of diamond significantly affects its price. However, Clarity, Cut & Carat (weight) also affects the price of diamond significantly.
Diamond is the only gemstone for which quality grade has been mentioned internationally and there is a standard price for different qualities of diamonds listed by Rapaport (http://www.diamonds.net/Prices/RapaportPriceLists.aspx). Rapaport is the primary source of diamond prices used by dealers to establish diamond prices in all the major markets. So, one can say that rapaport is practically the MRP (maximum retail price) list of all qualities of diamonds. However, mostly, one can get certififed diamonds below rapaport price in market.