Gordon Parks’s images of everyday American life under segregation were first published in 1956, one year after Rosa Parks refused to give up her bus seat in Montgomery, Alabama. By then, the bus boycott she had triggered was transforming the fight for civil rights into a national movement, and thrusting a young minister called Martin Luther King into the spotlight.

Parks’s shots challenge commonly held assumptions about segregation – chiefly, that it prevented any physical contact whatsoever between black and white Americans. The photographer, who also directed the 1971 blaxploitation detective movie Shaft, followed three related families – the Thorntons, the Causeys and the Tanners – in their work, home and church lives near Mobile, Alabama.

Untitled, Shady Grove, Alabama, 1956. Photograph: Gordon Parks/Courtesy of and copyright The Gordon Parks Foundation

His shots, about to go on display at the High Museum of Art in Atlanta, provide an intimate and surprisingly colourful look at racial division in the US at the time. Called Gordon Parks: Segregation Story, the exhibition consists of 40 colour prints rediscovered in 2012, six years after his death. The extended family he shot had first come to public attention half a century earlier, in a photoessay Parks did for Life magazine under the title The Restraints: Open and Hidden.

While some of Parks’s images do show the “Colored” entrance to a department store or an ice-cream stand, the exhibition is evidence that the notion of total separation was actually a fiction. Take his images of a black woman holding a white baby in an airport, and of two black boys and a white boy playing with guns. They reveal an equally true, if paradoxical, fact about segregation: blacks and whites mixed constantly, as the needs of employment, work or even play demanded.

Despite de facto segregation still being glaringly prevalent across the US today, Americans are more comfortable thinking about it as something that happened long ago. Black and white photographs help create that sense of distance, which is why Parks’s use of colour is so important: segregation no longer feels as if it’s from some distant, unrecognisable past. Even when Parks became Life magazine’s first African-American photographer, black and white was the dominant medium. If colour made his essay stand out then, the effect is even more striking today.

Airline terminal, Atlanta, Georgia, 1956. Photograph: Gordon Parks/The Gordon Parks Foundation

Although Parks was best known for Shaft, he was also an accomplished author, film-maker, composer – and photographer. Born impoverished and in segregation in 1912, he taught himself photography with a camera he bought from a pawn shop, going on to work for the Farm Security Administration and Life magazine. He then became the first black film-maker to direct a Hollywood film based on his own bestselling novel, The Learning Tree. And through it all, he kept experimenting with photography, which he saw as his “‘weapon of choice for social change”. His vibrant, disturbing images show just how effective a weapon it was in his hands.