Merry Christmas! Or perhaps a Happy Boxing Day would be more appropriate.
I've been wanting something like this for working out colors and markings for some time and thought you might find it helpful, too. After looking at a number of breed registration forms, I went ahead and created an expanded color and markings sheet from scratch.
I drew a body type that should cover most light horses, grouped the legs into what I hope makes logical sense, and added both a view of the tummy and a view of the back. The top and bottom views can be helpful if you want to create pinto markings that wrap around the body smoothly.
Micron inks on Como sketch paper, digital cleanup and finishes done in Paint Shop Pro 7.
The model horse has a generic mane and tail, alter them to fit your OC.
The inner legs have the "chestnuts" visible to help with orientation.
Download for the very large .png file.
Good for printing and coloring-in with the medium of your choice, or for digital coloring.
Edited to fix my error on the label for near and far sides on the legs.