Only the males have the red colouring; the females have the same patterns, but with brown in place of red. Redfin bullies of both sexes have distinctive diagonal stripes on their cheeks.
Male redfin bullies are the most colourful freshwater fish in New Zealand, with bright red markings on the dorsal, anal, and tail fins, as well as the body and cheeks. Additionally, males have a bluish-green stripe on the outer edge of the first dorsal fin.