From:
[email protected] (Jason Kennerly)
Methamphetamine in its pure hydrochloride salt form is colorless. However, products on the market today are often not colorless. The following is a table of some common impurities and the colors associated with them. Note: There is no doubt a segment of the dealers who will add food coloring or some other such color to their drug to make it more appealing, with the philosophy that a brightly-colored product may sell better than an off color product. This is relatively uncommon however.
RED: The product was made from pseudoephedrine, and the red coloring of the tablet was not adequately washed away (it is difficult)
ORANGE: Ephedrine sulfate was used, and some of the sulfate was reduced to sulfur.
PURPLE: Iodine from a phosphorus-iodine reaction was not washed out.
GREEN: Copper (or other metallic) salts somehow made their way in to the mixture, probably due to the reaction vessel used in the manufacture.
BROWN: Oxidized red coloring (see above), or tablating agent was present in the reduction
