light brown vs topaz

light brown and topaz both are nouns.

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

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

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

light brown (noun)	topaz (noun)
a brown that is light but unsaturated	a light brown the color of topaz
	a mineral (fluosilicate of aluminum) that occurs in crystals of various colors and is used as a gemstone
	a yellow quartz