light brown vs dun

light brown and dun both are nouns.

Word	Noun	Adjective	Verb	Adverb
light brown	Yes	No	No	No
dun	Yes	Yes	Yes	No

As nouns, dun is a hyponym of light brown; that is, dun is a word with a more specific, narrower meaning than light brown:

Other hyponyms of light brown include tan, topaz, fawn, grayish brown, greyish brown, beige, ecru.

light brown (noun)	dun (noun)
a brown that is light but unsaturated	horse of a dull brownish grey color
	a color or pigment varying around a light grey-brown color

light brown (adjective)	dun (adjective)
	of a dull greyish brown to brownish grey color

light brown (verb)	dun (verb)
	make a dun color
	cure by salting
	persistently ask for overdue payment
	treat cruelly