lavender vs lilac

lavender and lilac both are nouns.

Word	Noun	Adjective	Verb	Adverb
lavender	Yes	Yes	No	No
lilac	Yes	Yes	No	No

As adjectives, lavender and lilac are synonyms defined as:

Other synonyms of lavender include lilac-colored.

lavender (noun)	lilac (noun)
a pale purple color	any of various plants of the genus Syringa having large panicles of usually fragrant flowers
any of various Old World aromatic shrubs or subshrubs with usually mauve or blue flowers; widely cultivated

lavender (adjective)	lilac (adjective)
of a pale purple color	of a pale purple color