Bettas often live around two to four years, and colour is one of the places those years show first. A red fish may soften toward rust, a blue fish toward grey at the edges, and neither change means illness on its own. What separates ageing from trouble is how fast the change arrives, how it spreads and what arrives with it.
The ageing pattern: slow, even and well behaved
Ageing fade creeps. Across months the colour loses depth fairly evenly over the body and fins, in step with slower swimming, longer rests and a calmer response to the world. Through all of it the fish keeps his side of the bargain: he still comes to food eagerly, spreads his fins when displaying, holds his body condition and breathes evenly at rest. The change also stays consistent from week to week, so a photograph from spring and another from summer differ gently rather than dramatically. A betta fading this way is growing old in the ordinary pattern, and your job is comfort and observation rather than intervention. He may also flare less often at his reflection or at the world outside the glass, and that quieter display belongs to the same slow pattern when appetite and condition hold.
The pattern that needs investigating
Colour loss deserves attention when it breaks the ageing pattern in any of three ways. It may arrive fast, noticeably deeper over days rather than months. It may spread unevenly, leaving pale patches, a washed-out head or one dull flank beside bright colour elsewhere. It may also travel with company: clamped fins, a thinning body, reduced appetite, new pale marks or growths, or breathing that looks harder at rest. Any of those companions turns a colour question into a health question. Colour alone rarely names a cause: water quality, infection and other conditions a vet investigates can all sit behind a similar pale fish. Treat the change as a prompt to gather evidence rather than as an answer.
Test the water before anything else
Run the water tests first, on the day you notice the change. An old betta shows slipping conditions early, and ammonia or nitrite where neither should be, a temperature that has drifted low, or a filter that has slowed can each leave a fish pale and clamped. Correct what the tests show, gently and in steps, then watch his colour and appetite across the following days. Colour that returns as the water settles has given you its explanation. Colour that stays lost in clean, warm, stable water, or signs that gather rather than ease, deserve advice from an aquatic vet, who can examine the fish and consider causes beyond the water.
A monthly photograph settles arguments
Memory is a poor colour judge, so set up one photograph a month and keep the setup fixed. Photograph him in the same part of the tank, under the same light, at a similar time of day, against a similar background, and file the shots in date order. Review the series rather than any single frame, because lighting tricks in one shot can invent a change that the series then cancels. Write one line beside each photograph covering appetite, fins and breathing, so the visual record and the behaviour record stay together. Keep the camera at the same distance too, because a closer shot deepens colour in the frame and can fake a recovery that the wider series then contradicts.
That dated series, kept in KinsLe's Pet Passport with his water results, gives a vet a timeline of the fade instead of a single worried snapshot.