Welcome to the community
Can you post a photograph? Is this coloration change permanent? It is quite normal for fish to change color, aggression, stress, illness, breeding will often result in a fish changing color. However, a fish shouldn't change color completely unless it is maturing, in that case, many fish to change color as they get older. Normally, young fish are a completely different color, they normally have camouflage type colors. Anyway, if you can take some photographs, I'm sure we can help you