There are three layers of colour on discus: The base colour (which usually ranges from cream to red-brown), the secondary colour (a metallic colour, usually a blue or green colour) and the black pigment that makes up the black vertical bars and allows the fish to darken and lighten at will.
Most discus strains have either a golden or reddish base colour. The secondary colour is often striped down the sides of the fish, although many strains (such as 'solid cobalt' or 'blue diamonds') have secondary colour that eventually covers most or all of the fish's body.
There are no rules or authorities on what constitutes a unique colour variety or what to call it. A particular form may or may not breed 'true' (with offspring very closely resembling the patterns of their parents.) Generally all of the common, established forms breed true. The exact patterning of the secondary (blue/green) colour is like a fingerprint; it develops chemically rather than being set precisely by genetics . The offspring of two 'spotted' discus will likely have spots, but not in the exact same size/position as their parents.
Notable colour varieties:
- Brown: The most common colour form in the wild; these fish have a brownish base colour with minimal stripes of secondary colour only along the head and fins.
- Blue/Green: Similar to the Brown, but with more secondary colour (either bluish or greenish.)
- Royal Blue: The secondary colour forms stripes across the entire body, with a golden base colour. These splendid fish are the basis of many of the developed colour strains, and are primarily responsible for the early fame of discus. Royal Blues can usually be readily distinguished from selectively bred colour forms by their less even base colour, with the golden colour becoming a brighter yellow around the breast area.
- Red Spotted Green: A reddish base colour with greenish secondary colour with 'holes' in it (producing spots of the red base colour showing through.) This handsome colour form is extremely rare in the wild, but is produced by several breeders.
- Heckel: Possibly a separate species, Heckels are identifiable by two vertical black bars that are much thicker than the others.
Common Bred forms:
- Red Turquoise: A red-brown base colour with stripes of blue-green secondary colour, normal black pigmentation (bars).
- Solid Cobalt: Golden or light brown base colour, but when fully mature covered with a blue secondary colour. Black pigmentation may be normal or incomplete (some vertical bars missing.)
- Blue Diamond: Essentially a 'solid cobalt', but the black bars have been completely removed through selective breeding. The reduction in black pigment gives these fish a bright, lighter blue colour than most 'solid' discus.
- The Pigeon Blood mutants: These fish have a gene that disrupts the distribution of the black pigment. As a result, they lack vertical black bars (but often have 'pepper'). The lack of black pigment makes their base colour much lighter and brighter; as a result, discus with this mutation may show brilliant red or yellow (or even pale cream) primary colour. Most of these strains are no longer called 'pigeon bloods' per se, but are easily identifiable by the bright base colour, pepper, and lack of black vertical bars. All pigeon bloods are the descendant of a single fish found in Eastern Asia in the 1980s. Since the trait is dominant and appears to be controlled by a single gene, fish bearing this mutation can be crossed with any other colour strain to produce novel new 'pigeon blood' types. Pigeon bloods do have one drawback: They cannot darken at will (as normal discus can). This can make it difficult for them to raise fry, which are attracted to their parents by seeking out a dark object. (Normal discus darken when spawning or stressed.) The fish shown at the top of this document is a pigeon blood. (High quality pigeon blood types have few or no 'pepper'.)
- Snake-skins: These fish have a mutation that makes their patterning 'tighter'; as a result, they have about twice as many black vertical bars, but also have tighter, finer secondary colour patterns than normal discus.