Because the U.S. Food and Drug Administration requires all approved prescription and over-the-counter drugs to have unique appearances, you can identify a pill by its color or size by searching one of several online databases, advises About.com. Each pill's distinctive identity is a combination of its shape, pattern, color and imprints. Though searching by the imprint should positively identify the pill or capsule, you can also search based on color or size and then browse the images for a match.
The FDA requires all covered drugs to have an imprint, selected by the drug manufacturer, to identify the drug product, notes Drugs.com. An imprint is a letter, number, combination of letters and numbers, symbol, or logo. If the pill, tablet or capsule has no imprint, then pill identification by color or shape alone is difficult. In this case, the pill is not in any of the online pill identification databases, because the lack of imprint indicates that it is a vitamin or another dietary supplement, which does not require an imprint, or it is not an FDA-approved drug. Pills without imprints might be counterfeit drugs or adulterated formulations, illegal drugs like ecstasy, medication from another country, products used in research, or candy.