Donkeys, zebras and mules all differ somewhat from horses in conformation. The most noticeable difference is of course the ears. Donkeys ears are MUCH longer in proportion to their size than a horse's. The necks are characteristically straighter in the longears, and most donkeys and all zebras lack a true wither. The croup and rump are also a different shape in the donkey and it's hybrids, lacking the double-curve muscled haunch. The back is straighter due to the lack of withers. Dipped loins  or severely swayed backs are a conformation fault, unless in old animals or brood jennies who have produced many foals, and not due to genetic factors.
                The mane and tail in the donkey are coarse. The mane is stiff and upright, rarely laying over and the tail is more like a cow's, covered with short body hair for most of the length, and ending in a tasseled switch. Donkeys do not have a true forelock, although sometimes the mane grows long enough to comb down between the ears toward the eyes. Because the mane is stiff and sometimes flyaway, many donkeys, especially show stock, wear their manes clipped short or shaved close to the neck.
                Hoof shape varies as well, donkey hooves are smaller and rounder, with more upright pasterns. The legs should have good bone, but many donkeys of common breeding may appear to have long thin legs with tiny feet. Larger Asses such as the Poitou or Andalusian types may appear opposite, with huge, heavy shaggy legs and large round feet. Good legs and feet are essential for breeding Mules, as a good foot is much preferable to a large body on tiny stick legs and feet.
                The vocal qualities are the frequently remembered differences in the long-ears. The donkey's voice is a raspy, brassy Bray, the characteristic Aw-EE, Aw-EE sound. Jacks especially seem enjoy  braying, and will "sound off" at any opportunity.
  Although many donkeys are the familiar gray-dun color, there are many other coat shades. Most donkeys, regardless of coat color, will have dorsal stripes and shoulder crosses, dark ear marks, as well as the "light Points" - white muzzle and eye rings, and  white belly and inner leg. Leg barring ("garters" or "zebra stripes") may be present as well. Small dark spots right at the throatlatch, called "collar buttons" are a good identifying marking and occur occasionally. These typical donkey markings may be passed on in part or whole to Mule or Hinny offspring.
Colors in the donkey range from the gray shades of Slate Gray (Gray-dun)  to brown, a rare bay (though not as red-toned as in horses) , black, light-faced roan (both red and gray), variants of sorrel, the blue-eyed Ivory (also called cream or white-phase), Frosted/spotted White, and a unique Spotted pattern.  True horse pinto, horse aging gray, horse appaloosa, palomino and buckskin do not occur in the donkey.
The more unusual colors are the Dappled Roan, where the face and legs are light and the body is marked with "reverse" dapples (dark spots on a light background, as opposed to the horse dapple where the dapples themselves are light on dark), frosted gray (with light faces and legs and some white hairs in the coat) the pink-skinned, blue-eyed Ivory white, and the frosted spotted white. The frosted spotted is an apparent combination of a graying or roan with the spotted pattern,  and can throw either more FSW, spotted, or frosty roan colts. The animals are best defined as a spotted animal where the skin is spotted but the color does not necessarily show through on the coat (it has roaned or "grayed" out) . Frosted spotted white (FSW) can be identified from Ivory white by checking the skin around the eyes and muzzle. Ivory (creams)  will have blue eyes and true pink skin, while FSW will have dark eyes, dark "eyeliner" and           dark spotting on the skin.
Another unusual variant of the spotting line is the "tyger spot" pattern. These donkeys vary from the typical large spots over the ears, eyes, and topline. The body will be covered with small round spots resembling the appaloosa type.