It is - not down to the shade, no, but the base color and general shade for eggs is always written in the standard. You can never be precise on the shade of course - but an Ameraucana should always lay blue, just like a Marans should lay some darker shade of brown.
x2 on what CochinBrahmaLover and poltroon said.
A lot of people take mutt offensively but honestly, in all reality, it's a word and not an insult. Fact of life is that they are mutts 90% of the time and there's no way to get around that. Hatchery stock especially has been obviously out-crossed...