Hello and welcome to MFK!
Could you be more specific please? Often, colors will "wash out" at times with a fish. Stress, water quality, breeding habits, etc. will either enhance or diminish the intensity of the colors.
Have you tested your water? What are your readings? Have you done a water change, added new fish, lost a fish, added decorations, etc?
I am sure everything is OK, but anytime something appears to be different than what you are used to, check your water right away. Also, give your fish a visual physical...look for unusual spots, bumps, colors, swelling, etc.
The group of people here combined has been through about every possible situation in fish keeping. If you reply with your specifics, someone will know what's up
Again, welcome!