As an app its a bit raged around the edges but its easy to figure out how to use it (the link to the instructsions doesnt work) and this virtual equine paper doll suprisingly addictive.
You start with a basic body outline and then you click to choose body color, mane, and tail colours.
Then drag and drop markings and tack onto your horse.
Now screen print to save the image.
This is a must for a boring day in the office!