Betta fish come in many colors and patterns. The Betta also can change colors as it matures. If your fishy is sick, he or she can also exhibit color changes and these are the ones we want to be able to identify as harmful in order to find the correct treatment and cure.
Healthy fish usually exhibit a vibrant color. If he is sick, his color may look paler, the color may be dull, and his coloring may even turn gray.
For example, if you buy your fish at the petstore and he is tiny, chances are that he is only a few months old. The males can grow quite a bit, but are usually larger than the tiny little females even when they are in their teeny little cups of water at the petstore before you adopt him or her.
At this age and size - you may decide on a betta fish that seems almost clear or all one color, but after a few months, he gradually changes to a colorful solid color or spotted or splotching of colors - like red and green, for instance, or blue. The colors usually get darker rather than lighter. Of course, any white spots are probably not natural and may indicate a state of disease such as “ick” or “ich”. Red spots, on the other hand, if not the innate pattern of color on your fish could indicate the disease of septicemia or ulcers.
To keep your betta fish in his tip-top shape healthwise and thus at the proper coloring that nature intended your particular little guy or girl to be, keep him healthy and happy and blowin’ bubbles with clean, conditioned water at the right temperature with an appropriate water heater and check it with an aquarium thermometer to make sure it is kept at a consistent temperature. Sudden changes in water temperature can be stressful on your fish. Stress is one of the biggest culprits that cause disease in fish. Cold water is also responsible for some fish diseases. The biggest killer of fish from stress, though, is bacteria and other garbage in the water such as old, uneaten food and urine and fish poopie that changes into ammonia in the water if not kept changed and filtered. Keep his water clean and aerated with a good filtration system in a good-sized aquarium. Feed him regularly with the correct food specific for Betta fish.
Some Betta fish foods actually have color-enhancing properties! They provide appropriate and delicious nutrition to your Betta buddy and also help maintain their natural coloring so they can proudly strut their stuff around the aquarium! (See Hikari Betta Bio-Gold as a suggestion.)