Pygmy Corys Changing Colour

[laxation]

This morning the spot on my hastatus cory was much brighter than normal, and one of his eyes was yellow-ish rather than the black it normally is.
After swimming a bit, his colour has come back completely.

Anyone know why this happened?

 

[Ben M]

hi, had the light just come on? fishes colours become more pale during the night.