mellow out vs mellow

mellow out is not an adjective while mellow is an adjective.

Word	Noun	Adjective	Verb	Adverb
mellow out	No	No	Yes	No
mellow	No	Yes	Yes	Yes

As verbs, mellow out and mellow are synonyms defined as:

Other synonyms of mellow out include melt.

mellow out (adjective)	mellow (adjective)
	slightly and pleasantly intoxicated from alcohol or a drug (especially marijuana)
	unhurried and relaxed
	having a full and pleasing flavor through proper aging
	softened through age or experience

mellow out (verb)	mellow (verb)
become more relaxed, easygoing, or genial	make or grow (more) mellow
	soften, make mellow
	become more relaxed, easygoing, or genial

mellow out (adverb)	mellow (adverb)
	in a mellow manner