I would go with the appropriate color. The likelihood of finding a cancer ribbon fabric produced in each cancer color is slim. Too expensive to produce by the fabric companies and then not to be purchased by shops. Esp the more obscure color of ribbons. Frankly, i am not sure all cancer patients want to draw attebtion to their situation via a ribbon. Maybe even appliques in the color would suffice if one wants a ribbon. My 2 cents.
Sandy