In addition, each of the 3 may have differ in intensity; they may lighten or darken.
So, for example, you may have a chocolate, white and tan Pom that is about 1/3 of each, but then as an adult, he may be primarily chocolate brown
with the white growing in much more on the chest and the tan barely visible.
Some colors (or markings, more accurately), are expected to really transform; for example, sable, which is dark tipped hairs.
On this tri-color Pom (right; below on mobile), that is tan, white and sable, that sable was most likely more prominent when the Pom was a young puppy. Now, at almost 1 years old, color will stay relatively the same.
Can You Breed for Tri Colors?
Loki, 11 months old; Photo courtesy of David Bonn