1) One of the three primary colours of paint. When mixed with yellow, it makes green, and when mixed with red, it makes purple. It is opposite orange on the colour wheel.

2) One of the three primary colours of light. When mixed with red, it makes magenta. When mixed with green it makes cyan. It is opposite yellow on the colour wheel.

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In music the blues is about redemption. Not depression.

'blues' were originally known to intravenous drug users as azure-colored instant-release 10 mg oxymorphone, manufactured by ENDO. These were rightly considered the holy grail of pharmaceutical opiates before being discontinued due to problems with black market diversion and robberies. Many users ranked them more euphoric than heroin. They are cited in many works of fiction, notably Drugstore Cowboy.

a slang word for oxycodone 30 mg or a roxicodone 30 mg

UK slang, gang related / region specific:

Endeering term used for friends with business links, particularly in a few specific areas such as Streatham (blue town), Tottenham, and Cambridge. Used in place of "blud". Can get you in trouble around Woolwich and Hackney

Eiffel 65's song "Blue (Da Ba Dee)," that was released in 1999, is a popular Eurodance song which peaked at #2 on the Billboard Hot 100 in the United States, and reached #1 in 17 countries