My two cents. I got interested in this color change behavior of koi when I noticed long term color changes in esp. kohaks and short term changes when I treated Shiros in a white tank, which would fade sumi to light grey in seconds.
Signals from the fish's nerves and or release of hormones can rearrange the chromatophores whith is common with cold blooded creatures. Alteration of surroundigs such as water temperature and water quality, nutrition and fish's disposition seems to effect the different layers of chromatophores thus changing pigment intensity or loss of pigment. Changes can happen in seconds or can be a long term change. This is a phenomena in the balance between differentiation and apoptosis (ordered death process) of chromatophores. Works for me at least. |