Why do guppy colors fade?

Guppy color fading may come from unsuitable temperature, poor water quality, poor nutrition, or lack of light. The best growth temperature is 22 to 26 C; if too low, they easily feel discomfort and may fade, so raise the temperature with a heater when needed.

Also, poor water and poor nutrition affect color, so keep water quality good and feed balanced nutrition. To avoid fading, give about 3 hours of light per day.