The answer to this question depends on what you mean by ‘colours’. Fishes are, of course, covered in scales and these come in an incredible variety of colours and patterns. The reason why these fishes have different colours and why they change their colours, however, has more to do with the life of fishes and how they interact with their environment than it does with their colouration per se.
The types of Fish
As you know, fish are generally classified by their appearances. The classification of fish is based on their sizes and shapes. A few types of common fishes are given below: 1)Salmon, 2)Bass, 3)Herring 4)Pike, 5)Trout, 6)Eel and 7 )Carp. They all belong to diverse classes, but appear differently in shape and size.
Combination Of Bright Colours
Fishes tend to be vividly coloured, in fact, some species of fish that live close to coral reefs are among some of the most colourful living creatures on Earth. Fish and other sea creatures are made up of a large range of natural pigments that give them their colour. Pigments found in red, yellow, brown and black colours range from compounds such as carotenoids (found in plant leaves), to xanthophylls (mainly from leaf algae) and many more.
Proportion And Contrast
This is basically a result of how sunlight reacts with their bodies. The light that penetrates their bodies is broken down by pigments and structural coloration. In order to get structural coloration, a fish needs to have its skin composed of tiny, tightly-packed cells called chromatophores. These act as filters that can reflect or absorb certain wavelengths (colours) of light. Structural coloration works along a simple principle: if you want something to look red, make it look bright white first!
Body Shape And Colours
The most common shapes are bar, leaf, and butterfly. Bar-shaped fish are usually silver in colour and will fluoresce blue under a UV light. Leaf-shaped fish have an iridescent sheen of blues, greens, or yellows; these fish will fluoresce purple under a UV light. Butterfly-shaped tetras come in many colors but their main color is usually dark with metallic reflections of blues or purples.
Fish usually eat plankton, plants and each other. There are three main types of fish: piscivores (fish eaters), planktivores (plankton eaters) and detritivores (detritus eaters). Piscivorous fish include sharks, tuna, swordfish and salmon. Planktivorous fish include herring, sardines and anchovies. Detritus feeders include cod and flatfish like sole.