cerulean vs sapphire

cerulean and sapphire both are nouns.

Word	Noun	Adjective	Verb	Adverb
cerulean	Yes	Yes	No	No
sapphire	Yes	Yes	No	No

As nouns, cerulean and sapphire are synonyms defined as:

Other synonyms of cerulean include azure, lazuline, sky-blue.

cerulean (noun)	sapphire (noun)
a light shade of blue	a light shade of blue
	a transparent piece of sapphire that has been cut and polished and is valued as a precious gem
	a precious transparent stone of rich blue corundum valued as a gemstone

cerulean (adjective)	sapphire (adjective)
of a deep somewhat purplish blue color similar to that of a clear October sky	of something having the color of a blue sapphire