I don't have a horse with this gene, so again, I'll be sharing pictures of other people's horses, and linking to the site I found them.
The most common color associated with this gene is Silver Dapple. These are black horses (E? aa) with at least one dominant copy of silver (ZZ or Zz). The silver gene only affects black pigment, so this gene can easily hide on a red horse, like Agouti can. It will have an effect on a bay horse, and often silver bays are mistaken for chestnuts. Like with all other genes, you can of course stack these up, resulting in colors like Silver Amber Champagne Dun (or E? A? crcr Ch? D? Z?). Again, those question marks represent places where the other allele is either unimportant, or unknown.
Here is a great example of the silver gene on a black horse. This horse's color would be called silver dapple, even though this horse shows little if any dappling.
the horse below would be the typical appearance that the color earned its name for.
He's obviously a silver color with dapples. And I have to mention here that I just love ponies.
Of course, on a bay, the horse would have a very different appearance. The black pigment at the points (legs, muzzle, tips of ears) is diluted to a brownish color, sometimes as light as a redish color, while the mane and tail again show the most dilution. This horse is an easy to identify silver bay, and you can see how easy it would be to confuse it with a chestnut.
Here is an example of a horse that could easily be mistaken for a chestnut or sorrel.
The horse below is a flaxen chestnut, compare how similar his color is to the horse above.
Because silver only affects black pigment, in true red based horses, such as chestnut/sorrel, palomino, or gold champagne, there is no effect on the horse's body color. These horses are carriers of the gene, and could, if bred to a black based horse, have offspring who exhibit the silver trait. In the past, silver has "come out of nowhere" because of its ability to hide on red based horses, and mistaking the genetics of many silver bays. As a dominant gene, only a single copy is required for a horse to exhibit this color, and at least one parent must have the gene to pass it on, but the ability of this gene to hide has made tracking it through pedigrees difficult. Now that there is a DNA test for silver (Z) it has become much easier to breed for this color.
Whoops! Almost forgot to add your daily gene test!
So, what color is this horse:
Ee AA gg dd crcr CHch Zz?
Two right answers (the base color with modifiers, or the horseman's term for it).