The colour in the brown fat is due to: Its larger capacity for generating heat; Large number of mitochondria present; A high concentration of iron containing cytochrome pigments; Presence of chromatophores.

Brown fat is found in many species of mammals. The brown fat is capable of consuming higher rate of oxygen and producing a large amount of heat. The reddish brown colour of fat is derived from the iron-containing cytochrome pigments in the mitochondria, the essential part of the oxidising apparatus of brown adipose tissue. With its rich supply of mitochondria, it acts as the metabolic heater applied directly to the bloodstream.