Old Colony vs Bay State

Old Colony and Bay State both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old Colony	Yes	No	No	No
Bay State	Yes	No	No	No

As nouns, Old Colony and Bay State are synonyms defined as:

Old Colony and Bay State: a state in New England, with capital Boston; one of the original 13 colonies

Other synonyms of Old Colony include MA, Mass., Massachusetts.

Old Colony (noun)	Bay State (noun)
a state in New England, with capital Boston; one of the original 13 colonies	a state in New England, with capital Boston; one of the original 13 colonies