college man vs college boy

college man and college boy both are nouns.

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

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

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

Other synonyms of college man include collegian.

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