just go to any site with lots of fish profiles and browse through the pictures until you find your fish. then find out what the male looks like and what the female looks like.
because you dont even know what kind of fish they are, im gonna guess that they are fairly common. in this case, heres a list of possible fish you could have. just search google images for these names, i bet one of them is your fish.
australian rainbow
bosemani rainbow (sometimes spelled boesmani)
praecox rainbow
dwarf neon rainbow
irian rainbow
celebes rainbow (not likely)
or just go here: http://www.aquahobby.com/e_gallery.php
scroll to the "rainbowfishes" section and click each name until you find yours.
because you dont even know what kind of fish they are, im gonna guess that they are fairly common. in this case, heres a list of possible fish you could have. just search google images for these names, i bet one of them is your fish.
australian rainbow
bosemani rainbow (sometimes spelled boesmani)
praecox rainbow
dwarf neon rainbow
irian rainbow
celebes rainbow (not likely)
or just go here: http://www.aquahobby.com/e_gallery.php
scroll to the "rainbowfishes" section and click each name until you find yours.