Goldfish will change color as they mature.....Often when you buy a black moore...they will change color to solid orange or sometimes white.

Sierra

the colour change has happend in secounds though is this normal?

Although black is the most unstable color and "enhanced color foods" and ingrediants with spirulina will encourage orange coloring, that's odd that its instant. Are you sure its not just the metalic shine? Moors are velvety matte black, but some have a bronze or silver metallic belly.

strangly her colour is back to normal

With my experience, the Black Moors keep their black color throughout their life. However, when they change colors, it usually means that they are dying or already dead. Freaky? I know...