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So the way I think about the leopard complex is that every horse technically has a "blanket," and that patterning genes control the size.

I was reading about some recent findings in coat color mutation (there's a really cool blog called The Equine Tapestry, not sure if I can link it here), and it's thought that leopard spotting is actually one of the earliest color mutations. If I recall correctly, it affected the way dun (wild type for horses) by causing progressive loss of pigment. This may explain appaloosa color shifting (the weird color base coats sometimes turn on appys - ex: sometimes black based horses appear a metallic brownish copper) as well as varnish (progressive roaning, independent from the classic roan Rn-). It is recognized as one of the most ancient variations in color, and is depicted in Old World art. Again, super cool.

The dun dilution is related to the distribution of pigment within a hair, rather than the color of the pigment. In the recently published paper dun was described as "microspotting" within the hair follicle. This could be related to larger scale spotting found in later mutations - including leopard! So to try and tie all that together - leopard is a very old mutation of the wild-type. Dun dilution is caused by distribution of pigment within a hair, which very well may be a "micro" predecessor or large scale spotting patterns. Appaloosas have a couple of intriguing traits, such as shifts/dilutions in base coat color and progressive roaning.

So back to pattern distribution! Think of white areas as parts of the horse that color never reaches during development, rather than "lying over" the base coat. One copy of leopard (Llp L) causes an incomplete restriction of pigment, which produces the spots we're familiar with. Two copies (Llp Llp) completely limits pigment within the pattered area - these are the solid "snowcapped" blankets and few spots.

Patn is silent without leopard to work on (If you're curious, look of Reminic N Spots - he's actually a Quarter Horse whose sire carried Patn silently. When bred to a mare carrying leopard, who had been misidentified as classic roan, they produced a loud spotted foal). The actual distribution of white on a particular horse depends on conditions in utero, which is why clones' white markings don't match. This is true for placental mammals in general. Because of that - and some other factors we may or may not know about - the degree of expression (size and positioning of the pattern) varies between individuals. What is certain is that a horse without Patn has a minimal appaloosa pattern, a horse with one copy (Patn patn) has an obvious blanket, and a horse with two copies (Patn Patn) has a really big blanket. This really big blanket may cover the whole horse, or it may leave parts of the head, chest, and/or legs solid.

Hope that helps! It was always a little fuzzy for me until I really tried to understand how the genes worked. Can't promise it's 100% correct, but these are conclusions drawn on the research that's been done to date.

I kind of love appaloosas.

Interesting tangent: In fact, sooty may be described as "primitive marking without dilution," and if you look at dun (and panagre - think Pzerwalski's horse) as the primitive form then sooty is a variation of wild-type countershading.

Yep, near leopard is the term for almost a full leopard but not quite.