college boy vs college man

college boy and college man both are nouns.

Word	Noun	Adjective	Verb	Adverb
college boy	Yes	No	No	No
college man	Yes	No	No	No

As nouns, college boy and college man are synonyms defined as:

college boy and college man: a student (or former student) at a college or university

Other synonyms of college boy include collegian.

college boy (noun)	college man (noun)
a student (or former student) at a college or university	a student (or former student) at a college or university