The Mermin possessed the ability to change their skin colour. (PROSE: The Underwater War)
Coloured, spelled colored in America, was a term used to refer to black people in the 20th century. In Montgomery in 1955, it was an offence to to harbour "coloureds" in motels. On buses, a row of "colored" seats were separate from "whites". Yasmin Khan, a British woman of Pakistani heritage who had been mistaken for a Mexican by locals, was unsure if "coloured" just meant black and took a seat in the white section. By law, the seats on the middle section were only for "coloureds" if "white folk" did not need them. On 1 December, while travelling home from work, civil rights activist Rosa Parks famously refused to give up her bus seat when the bus became crowded, leading to her arrest, an event that the Thirteenth Doctor, Ryan Sinclair, Yasmin, and Graham O'Brien witnessed. Her arrest lead to the Montgomery Bus Boycott, and a further chain of events that would result in the abolishment of segregation a year later. (TV: Rosa)
In 1963, a sign hanging in the window of Mrs Smith's Shoreditch boarding-house read "NO COLOUREDS", which Ace seemed to be disturbed by, so she took it down and hid it. (TV: Remembrance of the Daleks)
The term "person of colour", or POC, at least in the United States, referred to any person who was not white. Rachel Edwards was not pleased to find only a couple of POCs in Matt Nelson's entourage of otherwise invariably white, cisgender, monosexual rich people. (PROSE: Head of State)
In 1913, Joan Redfern expressed disbelief to Martha Jones that a woman of her "colour" was really training to be a doctor. (TV: The Family of Blood)
The Cybus Industries Cybermen of Pete's World sought to remove human colour, amongst other things, to become identical. (TV: Doomsday)
Rani Chandra observed that the Blathereen were not the same colour as the Slitheen. (TV: The Gift)
Aboard the Teselecta, Jim reported that the art department wanted to "talk skin tone" whilst they were copying the form of Erich Zimmerman. Harriet did not trust the sensors and wanted to take a look personally, recalling an incident which saw them make Rasputin in green. (TV: Let's Kill Hitler)
Lucy Wilson recalled having been followed around a department store because of the colour of her skin. (PROSE: 8.46)
Olivia Steele had "flawless" caramel coloured skin. (PROSE: Exodus Code)