During the Vietnam War, the U.S. military used a series of herbicidal defoliants collectively known as "Rainbow Herbicides." These were named based on the colored stripes on their storage barrels, with Agent Orange being the most well-known. Each agent had a specific chemical composition and purpose, primarily for defoliation and crop destruction. Below is a concise overview of the main agents, based on historical records:

Agent Orange: A 50/50 mix of 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid). Used extensively from 1965–1970 to defoliate forests and destroy crops. Contaminated with TCDD (a highly toxic dioxin), causing severe health and environmental harm. Approximately 11 million gallons sprayed.

Agent Purple: Similar to Agent Orange, a mix of 2,4-D and 2,4,5-T, but with a higher concentration of 2,4,5-T. Used earlier (1962–1965) and contained even higher levels of TCDD. Less widely used due to limited production.

Agent Pink: Primarily 2,4,5-T, with little or no 2,4-D. Used in early test phases (1961–1965). Highly toxic due to concentrated TCDD. Limited use, mostly in experimental spraying.

Agent Green: Also composed mainly of 2,4,5-T, similar to Agent Pink. Used in small quantities during early stages (1961–1965) for crop destruction. Like Pink, it had high dioxin content.

Agent Blue: Chemically distinct, containing cacodylic acid (dimethylarsinic acid). Used for crop destruction, particularly targeting rice fields, as it was effective against grasses and grains. Did not contain dioxins but was toxic due to its arsenic content. About 1.2 million gallons sprayed.

Agent White: A mix of 2,4-D and picloram (4-amino-3,5,6-trichloropicolinic acid). Used from 1966–1971 as a longer-lasting alternative to Agent Orange, effective against hardwood vegetation. Did not contain 2,4,5-T or TCDD, making it less dioxin-contaminated, but picloram’s persistence raised environmental concerns. Roughly 5.4 million gallons sprayed.

These agents were part of Operation Ranch Hand (1961–1971), with over 19 million gallons of herbicides sprayed across Vietnam, Laos, and Cambodia. Agents Orange, White, and Blue were the most used, while Purple, Pink, and Green were phased out early due to limited supply or high toxicity. The dioxin contamination in agents containing 2,4,5-T (Orange, Purple, Pink, Green) caused the most severe health impacts, including cancers, birth defects, and neurological disorders, affecting millions of Vietnamese and U.S. veterans.