American spelling vs off-color

American spelling is a noun but off-color is not a noun.

Word	Noun	Adjective	Verb	Adverb
American spelling	Yes	No	No	No
off-color	No	Yes	No	No

American spelling (noun)	off-color (noun)
English orthography used in the United States (characterized by 'analyze', 'center', 'usable')

American spelling (adjective)	off-color (adjective)
	humorously vulgar
	in violation of good taste even verging on the indecent