blend in vs mix

blend in is not a noun while mix is a noun.

Word	Noun	Adjective	Verb	Adverb
blend in	No	No	Yes	No
mix	Yes	No	Yes	No

As verbs, mix is a hypernym of blend in; that is, mix is a word with a broader meaning than blend in:

Other hypernyms of blend in include blend, coalesce, combine, commingle, conflate, flux, fuse, immix, meld, merge.

blend in (noun)	mix (noun)
	the act of mixing together
	an event that combines things in a mixture
	a commercially prepared mixture of dry ingredients

blend in (verb)	mix (verb)
cause (something) to be mixed with (something else)	mix together different elements
blend or harmonize	add as an additional element or part
	combine (electronic signals)
	to bring or combine together or with something else
	mix so as to make a random order or arrangement
	open (a place) to members of all races and ethnic groups