Green’s Dictionary of Slang

1. (US) the colours, signified by a handkerchief, under which rival boxers fight.

1859		Matsell Vocabulum 125: COLORS. The respective handkerchiefs that each fights under.
1873		Sl. Dict. 125: Colour a handkerchief worn by each of the supporters of a professional athlete on the day of a match , so as to distinguish them from the partizans of the other side.

2. of ‘outlaw’ motorcyclists, one’s club emblem. Orig. used for the first such outlaws, the Hell’s Angels, consisting of an embroidered patch of a winged skull wearing a motorcycle helmet, the name Hell’s Angels, the name of the chapter (town etc) and the letters MC (motorcycle club); thus (N.Z.) run for one’s colours, to serve as a probationary member of the club.

1966		H.S. Thompson Hell’s Angels (1967) 17: The all-important colours [...] the uniform, as it were, the crucial identity.
1971		J. Mandelkau Buttons 32: At that time I had strict principles about busting other groups who were wearing the colours.
1985		J. Wambaugh Secrets of Harry Bright (1986) 174: ‘That dude sporting his colors?’ ‘Colors?’ ‘His bike jacket with the Cobras logo on the back.’.
2004		(con. 1980) N. ‘Razor’ Smith A Few Kind Words and a Loaded Gun 220: Gangs from all over London and the south-east would fly their colours and show-out at the Chick-a-Boom, and there were many fights.
2018		C. Hammer Scrublands [ebook] ‘Has the bike and the look, but I didn’t see any colours’.

3. (US) the insignia, e.g. a coloured bandana/headscarf/beads sported by members of the street gangs of Los Angeles, New York etc.

1977		A. Hoffman Property Of (1978) 7: I could read the Orphans’ colors on the backs of their leather or denim jackets.
1989		(con. 1982–6) T. Williams Cocaine Kids (1990) 60: We pulled off our jackets and showed them our colors [each gang distinguishes itself by wearing beads of a particular color].
1991		L. Bing Do or Die (1992) 226: The dude shot me. I wasn’t wearin’ no colors or nothin’, but my enemies knew I was out.
2000		W. Shaw Westsiders 32: Among the African-American gangs in LA, ‘colours’ — Crip blue and blood red — denote membership of the premier league of gang-banging.
2001		(con. 1990s) J. Miller One of the Guys 55: Triina said her aunts and cousins dressed her in gang colors from the time she was young.
2010		A. Steinberg Running the Books 232: Many of these men had traded gang colors for prison colors.

4. (US prison) in prison, a gang tattoo.

1992

Bentley & Corbett Prison Sl. 42: Earn Your Colors To have become a full-fledged member of a gang and have the right to get the gang’s tattoo.