Funny you should ask that question, I use to raise Golden and Sabino (pinto) colored Morgan horses and here something I found on the internet about sabino pinto coloring ...
"
Sabino White
Some white horses may actually be a type of pinto horse whose white markings are "fully" or "maximally" expressed, meaning, essentially, that the entire horse is one big white spot."
So yeah, I guess you are right, the Maltese is just one big white spot!
There are a lot more genes involved besides the spotting gene but I'll try to make it simple.
There are 2 basic base coat colors: black/brown and red/yellow but then there are other genes and gene modifiers that affect those colors. Some genes affect/dilute pigment color, some affect/dilute coat color and some influence the same color, adding some amount or a pattern of white spotting.
The maltese breed is an old breed and has been breeding the maximum expression of white to the maximum expression of white for years - they are homozygous for the extreme white spotting. So homozygous extreme white bred to homozygous extreme white = homozygous extreme white offspring.
Some Maltese do display a tan or lemon pigment around their ears, in horses, the extreme expression of pintos, generally have some pigmentation around the ears, flanks or tail.