"It's All In The Pigment"
The Liver and Blue colors are rare colors since they come from recessive color genes.The color of the hair is not crucial to classifying a dog as Blue or Liver color.
More significant would be the color of the “points” (eyes, nose, lips, paw pads) and skin. If these features are Liver rather than Black (except for the skin) then the dog is Liver.
If these features are Blue, then the dog is Blue, regardless of what the hair color may appear.
Conversely, if these features are Black (except for the skin), then the dog is not Blue or Liver even if the hair appears to be Blue or Liver.
Shih tzu are classified by thier nose colors it is the nose that determines color.
Black NOSE-Red,gold,silver,black,black and white.brindle
Blue NOSE-At birth they may look black and may take up to 8 months to change to blue,the nose will have a purple and blue shine.Blues come in many colors True blues,platinums,lavenders,Rose,silver,charcoal and brindles.
Liver Nose
the color of the nose pigment is liver,from dark chocolates to light creams.
Coat colors in a shih tzu can change from birth they usally lighten ,but some darken.