Why do shubunkins color turn black?

Shubunkin goldfish can experience changes in color due to various factors, including stress, water quality, or dietary changes. When exposed to poor water conditions or high stress levels, their colors may fade or turn darker, sometimes resulting in a black hue. Additionally, as shubunkins age, their pigmentation can naturally change, leading to variations in color. It's essential to maintain optimal tank conditions to minimize these changes.