|Image is from Flickr.com under a Creative Commons license|
This is Oslo and he is a Weimaraner. Except for the occasional exception, this breed only comes in one color. Oslo is that color. In the breed it color is called mouse-gray, but it is also known as fawn and Isabella. Here is Oslo's genotype:
Oslo is liver. Though he seems awfully pale for it, he is. The reason why he is so pale is due to a combination of the liver dilution gene and the next gene I will speak of. For Oslo to be the color that he is, he must be bb liver.
This dog is also blue. As I mentioned, the fawn color is caused by the action of two genes together: the liver gene and the blue dilution gene. Liver lightens the coat, and then blue lightens it even further until it is this light gray color with pale skin pigment to match and very pale eyes. For Oslo to be the color that he is, he must be dd blue.
Lastly, it's important to note that the blue and liver genes only act on black hairs in the coat. Due to that, Oslo must be solid black under the genes that diluted his coat. There are two forms of black, but recessive black is unusual and in Weims the black gene that is present is the dominant black gene. Since it doesn't appear that Weimaraners have any other form of the K locus, Oslo must be KK dominant black.
So, that's bb dd KK or mouse-gray/fawn/Isabella.