Well, my pictures aren't the most realistic (digital or traditional), but it helps if you draw a jawline and work on the eyes. If possible, it also helps if you look over a real picture of a wolf/lion/etc., as it might help you out more - atleast, if you want your pictures as realistic as they get.
With colors and markings, I try to get it as close to my character's as I can, to be honest, but it's completely on what you want to do. I'm sure a lot of the programs (MSPaint, FireAlpaca, Photoshop, etc.) have a RGB scale for colors and whatnot, which helps if you're making a character in FeralHeart, since you can just open it and blah, blah, blah.
Anyway, I hope this made sense to you.
-Wolfie