https://feral-heart.com/smf/index.php?topic=29488.0
This link may help you. Make sure you aren't using markings that were made by other users as it is considered art theft. Presets are encouraged to be totally original!
Make sure you're getting the creator of the marking's permission first.
Make sure you lock the transparency of the layer with the marking on it, paint it the color of the pelt, then make a new layer and put it under your marking layer. Then paint this one with the color you want for the marking.