play up vs highlight

play up is not a noun while highlight is a noun.

Word	Noun	Adjective	Verb	Adverb
play up	No	No	Yes	No
highlight	Yes	No	Yes	No

As verbs, play up and highlight are synonyms defined as:

play up and highlight: move into the foreground to make more visible or prominent

Other synonyms of play up include foreground, spotlight.

play up (noun)	highlight (noun)
	an area of lightness in a picture
	the most interesting or memorable part

play up (verb)	highlight (verb)
move into the foreground to make more visible or prominent	apply a highlighter to one's cheeks or eyebrows in order to make them more prominent
ingratiate oneself to; often with insincere behavior	move into the foreground to make more visible or prominent