My koi Half & Half, so named because his front is red and his back half is white, with an absolutely clean, straight division - as if someone picked him up and dipped him in a can of paint - one day he scraped his forehead / eye area on something rough, and scraped off the red scales.
So far (about a year) the area there is white. The red coloring has never come back.
Is that normal? They loose a scale / some skin and a colorless one replaces it? Or should the pigmented area fill in again?