Our Bio Diesel tanks at work have a Green Ring, with a B or BIO followed by a number IE B100 or BIO100 for 100% biodiesel. Our Boiler Tanks have B10 or BIO10 for 10% Bio and 90% low Sulfur Diesel. There is an argument going on About color coding for Clear, Red or Blue Diesel, which is pointless sense we can only use Clear Low Sulfur fuels.