All interstate shipments of the food seed such as wheat, corn, oats, rye, barley and sorghum bearing a poisonous treatment in excess of a recognized tolerance or treatment for which no tolerance or exemption from tolerance is recognized must be denatured by a suitable color to prevent use of such seed as food, feed or oil.
Many of the pesticides now come from the manufacturer with the dye or color added as a convenience to the operator; however, some seed processors prefer to mix the dye with the pesticide at the plant so that the desired color may be obtained. Most all treated seed are now colored, with the dye causing no apparent injury to seed germination or danger to personnel processing or using the seed.
These materials are listed on the label as inert ingredients. There is no requirement that the name of these materials be given. They are selected by the manufacturer and are usually neutral in pH, non-toxic to humans and cause no apparent damage to the germination of the seed.