Since this breed can be found in so many different colors, naturally it is very common for a Pom to have more than one in his coat. When there are two colors, this is referred to as 'parti' and technically white should be one of the colors.
The AKC 'prefers' that parti Pomeranians are white with another color. And a blaze (white running between the eyes and up over the forehead, as seen on this Pom (left; above on mobile) is preferred as well. Finally, in show ticking is not desired; ticking is a freckling of color on any white area. If the 2nd color is one in which 'self-coloring' is expected with solids (chocolate has a chocolate nose, eye rim, lips and paws pads, blue has blue, beaver had beaver) it is expected with partis as well. All others (orange, red, cream, white, etc.) should have black noses and black eye rims, lips and paw pads. Do keep in mind that
Poms do not fit what is desired in the show ring.
A parti Pomeranian may have a third color that may be little more than a tiny splash or may be quite visible such as a patches over the back. If just a splash, this may be classified as a marking and 'tri-color' is a choice when registering a pup.