lilac-colored vs lilac

lilac-colored is not a noun while lilac is a noun.

Word	Noun	Adjective	Verb	Adverb
lilac-colored	No	Yes	No	No
lilac	Yes	Yes	No	No

As adjectives, lilac-colored and lilac are synonyms defined as:

Other synonyms of lilac-colored include lavender.

lilac-colored (noun)	lilac (noun)
	any of various plants of the genus Syringa having large panicles of usually fragrant flowers

lilac-colored (adjective)	lilac (adjective)
of a pale purple color	of a pale purple color