It's a 'White skirt tetra' that has been subjected to a very cruel marketing practice of dyeing.

Basically, the colour of the fish is white. They have been artificially dyed to whatever colour.... they come in blue, pink, yellows, greens (basically any colour of the rainbow!). The fishes are put in an alkali solution and loose their mucous coat. They are then taken out (half dead), and put into a solution of coloured dye which eats into the skin. They then take the colour of the dye for sometime (many of the fish subjected to it will also die from the procedure later), but will eventually fade back into their original white colour.

While I will not get into the ethics of things here... I do not support the sale or purchasing of artificially dyed fish.... but I'm sure u didn't know they were dyed when you bought it. Just my opinion.

kev