There are 3 different types of noses in a shih tzu to determine pigment color.
1. Black nose (the most common shih tzu, you see these everywhere)- if the shih tzu has a black nose black eye rims, lips, pads, then you only go by the color of the coat to determine what color the dogs is.
** The Exotic and Rares**( the next 2, the color of the dog is determined by what color the nose is)
2. Liver- ( an Exotic Color ) If the shih tzu has a liver (brown/chocolate) nose, eye rims, lips, pads, it is a Liver Shih Tzu, it doesn't matter what color the coat is on these dogs its still a liver. anything except black. It cannot have a strand of black anywhere to be a liver.
3. Blue- ( A Rare Color),
most people have never seen these,
( only a few breeders produce these ) Sometimes blue can be tricky and hard to determine, Some noses are obvious and are light purpleish blue or light grey, but some are a real dark gunmetal grey and you may think its black. Most blue shih tzu's have grey eye rims, grey lips and foot pads. Some I have seen have a blue tint to their skin in some spots. A blue shih tzu can have any color coat. Just because the coat on a dog looks blue does NOT make it a blue shih tzu. Go by the Nose. You can tell the colors better in bright light outdoors. Compare a blue nose to a black nose to see the difference.
Both the Color Liver and Blue are dilute genes. You MUST have a Blue or Liver Shih Tzu or a carrier(parents, grandparents) to produce those colors.
4. ISABELLA(New to the Shih Tzu Breed and Extremely RARE COLOR)
In order for a dog to be dilute it must have the genotype dd. A dog which is Dd or DD will
have normal pigment(Black). The same dilution gene that causes a black dog to become blue also causes a liver dog to become isabella (aka lilac), which is a pale greyish/blueish brown. Dilution(blue) and liver are both recessive and relatively rare, so Isabella is a rarely seen colour. An Isabella dog will have the genotype bbdd (homozygous for liver, homozygous for dilution, blue). It is genetically impossible for a blue dog to have any black in its coat, or for an isabella to have liver.
Isabella: A dusty rose color coat with blue masking on face and a blue dorsal stripe. It has darker blue points. Some Isabella's are born completely blue at birth with the only noticeable difference from their blue littermates is a fawn shading appearing on the top of the head. By 10 weeks or so, the change is dramatic from blue to Isabella. They are a part of the blue gene group.
Lilac: Presently the rarest of all colors. It is a chocolate-blue dilute color giving the appearance of purple. Always found in dilute only. They are a part of the blue gene group.
5. DOBIE MARKED(Extremely Rare and Highly Prized Markings)-The TAN “Dobie” markings ON A BLACK PIGMENT, BLACK HAIRED PUPPY will appear in a very specific pattern in very specific locations on the body – a spot over each eye, on the jowls, on the lower legs, and under the tail. The marking under the tail is easily discerned at birth, whereas the other markings may not become noticeable until the puppy is about 2 weeks old. AKC will register the color and markings of a Shih Tzu with the “Dobie” markings as “Black with Tan Markings” Some “Dobie” marked Shih Tzu have been registered by breeders as “Black & Tan” rather than the “Black with Tan ”.
*** If you have a shih tzu with a BLACK nose, you have whatever the color your dog's coat is
If you have a shih tzu with a LIVER nose, you have a Liver Shih Tzu
If you have a shih tzu with a BLUE or GREY nose, you have a Blue Shih Tzu
An Isabella is trickier and not so simple, but the nose is usually a Rosie Tan.