This chapter discusses how artists use colour to communicate meaning by challenging perceptions of the world. It also discusses as examples, the work of three artists: the light artists James Turrell and Olafur Eliasson, and the sculptor Anish Kapoor. All three artists employ colour as a central feature of their work in large installations and well-known works of public art. Both Turrell and Eliasson have a keen awareness of art historical traditions, and each has credited a nineteenth-century painter as an influence. Turrell was inspired by Monet's famous Haystacks paintings, which studied light's role in constituting objects. In the 1960s and 1970s, Turrell collaborated with the artist Robert Irwin and aerospace scientist Edward Wortz on studies of visual phenomena such as ganzfelds. These are visual fields of uniformly coloured light, which affect viewers by producing blindness or even hallucinations.