If a shih tzu has cream almost white fur and a brown nose, what is its 'official' color? Is it still considered liver?

This site gives descriptions and examples of shih tzu coats. Hopefully, it can help you determine what color your animal is.

The Color of the Shih Tzu

Is your Shih Tzu a show dog or are you just curious?

I have found that solid colors generally don't do as well in the show ring as the partis but there are always exceptions to the rule.
Great link Cat, I would say OP's dog is a cream with liver pigment.