The APA Standard say Ameraucana eggs have a "distinctive blue shell coloration", yet birds are only judged on phenotype...not the eggs they lay.
There is no ideal "standard" egg shell color, other than "blue". "Shade" isn't mentioned in the standard or by the Ameraucana Alliance, only as preferences by individuals.
The color matters, because the official Standard says "blue". Beauty is in the eye of the breeder.
The Egg Color Reference Charts are only for referencing egg color as the name implies, but I know many assume they are for grading egg color as if one is preferred or ideal.