Due to events that people keep trying to take these to sell, from now on you have to note me for the original file if you want to make one for yourself. You can note me at FelisRandomis

Because the old one looked awful and needed to be redone DX

OC and SAI-
Go under your layers tab and click luminocity-transparency and that'll make it transparent.
PS-
Open it in Photoshop, change the layer from Normal to Multiply, and create a new layer underneath it.
Color on that new layer underneath it and you're good to go
Gimp-
Layer > Color to Alpha > White
New layer underneath, color that.

Please note, that these are free to color, and you can color them for others, but these are not available for you to make profit on unless I specifically give you permission to do so. Also, please give the proper credit...

Rabbit
Canine
House Cat
Dragon
Gryphon
Sugar Glider
Mouse/Rat