White fat was once believed to be the only significant adipose depot in adult humans. Advances in positron emission tomography (PET)/CT imaging have led to the rediscovery of brown fat in adults. Brown fat is metabolically active, and greater abundance is associated with lower adiposity, glycaemia and enhanced adaptive thermogenesis. Recent experiments in animals have identified a third kind of adipose, consisting of brown fat-like cells (known as ‘beige’ or “brite” adipocytes), which can be induced within WAT by cold stimulation. High brown/beige fat states reverse diabetes, obesity and hepatic steatosis in animals. The appreciation of the white-beige-brown fat spectrum has brought new hues to our understanding and interpretation of metabolism in humans. WAT browning and BAT whitening may underlie metabolic adaptation and pathologic transformation in physiologic and disease states. Knowledge on how fat changes colours and how such changes impact health and disease may illuminate novel therapeutic strategies in the combat against diabetes, obesity and related metabolic disorders.