Pale Black Widows?

[weary01]

hi, i recently added some long finned black widow tetras into my tank (couple months back) and i noticed that when ever i had the light on the tank their black marks on them would go very pale, at first i just thought they were getting used to the tank, and then i forgot about it but then noticed again they other day, right now its bout 9pm and the light is off and they have a very nice shiny black colour in them, but if the light were on they would go pale for the whole duration the light is on. any ideas?

the only thing i could link it with was if you have lighter coloured stones in your tank the fish tend to go pale, where as darker stones show a darker colour in the fish.

thanks

 

[angelfishguy]

i know these fish turn from black to grey as they get older but not sure about the whole light thing