Roan - A roan horse has a more or less uniform mixture of base coloured and white hairs.  Varnish marks are common on roans.  These are dark patches found often on the face, legs, stifle, above the eye, point of hip and behind the elbow.  The mare to the right is a typical roan.  As she is only a young horse, she may get lighter as she gets older.  Roans often become whiter as they age.  The second picture, of the same mare, shows spots on her rump.  Some roans have them, others do not.  She also has varnish marks. If a roan has no spots, it must have the characteristics to receive regular registration papers.

Snowflake - A base coloured horse with white spots ALL OVER its body is known as a snowflake.  It is easily confused with a lace blanket.  The horse to the right is a typical snowflake.  If it did not have white spots on its head and neck, it would be a blanket.  Many horses who are not Appaloosa also have white spots on their bodies which generally increase with age.  If a horse does not have the characteristcs, chances are - he's not an Appaloosa!

Characteristics.
The characteristics are - coat pattern, mottled skin, white sclera, and striped hooves.  You have already read about coat pattern, so here is a little about the others.
1. Mottled Skin.  The Appaloosa is the only horse to have this characteristic, so it is a very easy indicator of whether a horse is an Appaloosa or not.  It is not pink skin like that found under white markings, as it will contain dark and light areas, so is really a speckled pattern.  It is usually found in the anus region, spreading from the centre of the anus to the area around.  It is also often found on the udder or sheath.  It can also be found on the muzzle and around the eyes, extending over both nostrils and around the lips.
2. White Sclera.  This is a clearly visible white area surrounding the eye, where in other breeds it is brown.  It is not a characteristic when combined with a white face, as any horse with a white face may have white sclera.  Other breeds can show white when the eye is rolled back - do not confuse this with white sclera.
3. Striped Hooves.  Appaloosas are the only breed which may display bold, clear vertical stripes of light and dark without having white leg markings.  Be careful, however, as all breeds of horses can have stripes, as a result of an injury to the coronet band, or because of white markings.

The stallion, Cayuse Confewsion, showing a beautiful example of white sclera.  If you look closely, you can also see some mottling of the skin around his muzzle.