It's unwise to wash whites with coloureds, ie coloured clothes.

白色衣服不应该和有颜色的衣服一起洗。

youdao

It was against the law in Birmingham, Alabama, for whites and coloureds to play checkers together.

ECONOMIST: Black migration in America

Its backing is biggest among mixed-race coloureds, who make up about 9% of the 49m South Africans.

ECONOMIST: South Africa's opposition