It has be be white. And remember it only works on drugs metabolized via CYP3A4 enzyme, or one of a few others. It DOES NOT inhibit CYP2D6, so it is suitable for hydrocodone and codeine, to my knowledge.(though I take neither of these, it would reduce CYP3A4, reducing the amount of the inactive metabolites, allowing more morphine/hydromorphone to be created).