The experience of colour in Islamic visual culture has historically been overlooked. In this new approach, Idries Trevathan examines the language of colour in Islamic art and architecture in dialogue with its aesthetic contexts, offering insights into the pre-modern Muslim experience of interpreting colour. The 17th-century Shah Mosque in Isfahan, Iran, represents one of the finest examples of colour-use on a grand scale. Here, Trevathan examines the philosophical and mystical traditions that formed the mosque's backdrop. He shows how careful combinations of colour and design proportions in Islamic patterns expresses knowledge beyond the corporeal world, offering another language with which to know and experience God. Colour thus becomes a spiritual language, calling for a re-consideration of how we read Islamic aesthetics.