mix vs blend in

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

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

As verbs, blend in is a hyponym of mix; that is, blend in is a word with a more specific, narrower meaning than mix:

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

mix (verb)	blend in (verb)
mix together different elements	cause (something) to be mixed with (something else)
add as an additional element or part	blend or harmonize
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