Green’s Dictionary of Slang

1. amphetamine.

1965

P. Carstairs Concrete Kimono 227: He was [...] one minute ebullient, the next murderously low, and it made me wonder if he took snow or maybe purples.

2. LSD.

1969		R.R. Lingeman Drugs from A to Z (1970).
1971		E.E. Landy Underground Dict. (1972).

3. ketamine.

2001

ONDCP Street Terms 17: Purple — Ketamine.

4. (N.Z. prison) a 30 mg morphine sulphate tablet.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 148/2: purple n. 1 a 30mg morphine sulphate tablet .

5. (N.Z. prison) a halcion tablet.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 148/2: purple n. 2 a halcyon pill. [the next strongest after a blue].