Mexican green vs marijuana

Mexican green and marijuana both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mexican green	Yes	No	No	No
marijuana	Yes	No	No	No

As nouns, marijuana is a hypernym of Mexican green; that is, marijuana is a word with a broader meaning than Mexican green:

Mexican green: a particularly potent variety of marijuana
marijuana: the most commonly used illicit drug; considered a soft drug, it consists of the dried leaves of the hemp plant; smoked or chewed for euphoric effect

Other hypernyms of Mexican green include cannabis, ganja, marihuana.

Mexican green (noun)	marijuana (noun)
a particularly potent variety of marijuana	the most commonly used illicit drug; considered a soft drug, it consists of the dried leaves of the hemp plant; smoked or chewed for euphoric effect
	a strong-smelling plant whose dried leaves can be smoked for a pleasant effect or pain reduction