Actually, Dick, I think you'll find that die was normally added to product in order to identify it. The Texas Company, for example, used a copperish-red color in FIRE CHIEF and a purplish color in Sky Chief. One of the first things my Dad tought me when I started helping him make gasoline deliveries was to "always check the color of your product".
Originally posted by Dick Bennett:
Some gas pump company's ordered the glass tinted to block the effects of the sun turning the gas a milky color. As most oil company's added a dye to the gasoline, claiming that their gasoline was superior to the compitions. RE: GILMORE'S BLU-GREEN GASOLINE, or SIGNAL'S PUR PULL [purple].