The borders around appaloosa patterns are less uniform in width and placement than those on pinto patterns. This post gives a brief explanation of why this is true.
Shortly after I started this blog (2011), I made a series of posts about appaloosa patterns and skin color. I wanted to show how patterns with extensive white often had underlying dark skin. If you tuned in to this year's horse color seminar for BreyerFest, I used a different set of images to show this.
The horse is the leopard Appaloosa Lil Ricky Rocker. In the first image, I have removed his spots and the mottled patches on his nose. As you can see, without the spots, Ricky doesn't look like a white horse—he looks like a grey horse. Although the appaloosa patterns are genetically unrelated to greying in horses, from a visual standpoint artists are going to get closer to the mark if they conceptualize a patterns like leopard as a grey horse with colored spots, rather than a white horse with colored spots.
It is also not just that the skin under the pattern is dark (or primarily dark). With appaloosas, the white areas of the pattern are not always completely white. The mare at the top of this post is wet, so even her blanket looks dark. Her blanket looks closer to white—or rather, white-grey—when she is dry.
However, close examination shows that beyond the underlying dark skin, there are dark hairs mixed in even the whitest part of her pattern.
That's not to say that appaloosa patterns never have large areas of pink skin or entirely white hair. In fact, the area where the pattern is whitest on the mare pictured above is where you are most likely to see truly pink skin on an appaloosa. If you wet down a "nose-to-toes" leopard—a pattern that looks white with all-over colored spots—often the pattern on the skin will look like a blanket.
This important when considering mapping on appaloosa patterns, because mapping involves either a mismatch between the hair color (white) and the skin (dark), or it involves a blend of white and colored hairs. Unlike the typical pinto pattern, those two things are already going on with most appaloosa patterns. For that reason, mapping on appaloosas is not quite as straightforward as "what happens in the zone where white areas and colored areas meet." In the next post, I'll share some examples of how this works with appaloosas and how artists can use these details to create more convincing patterns.