earth color vs umber

earth color and umber both are nouns.

Word	Noun	Adjective	Verb	Adverb
earth color	Yes	No	No	No
umber	Yes	Yes	No	No

As nouns, umber is a hyponym of earth color; that is, umber is a word with a more specific, narrower meaning than earth color:

Other hyponyms of earth color include sienna, ocher, ochre.

earth color (noun)	umber (noun)
a colored mineral used as a pigment	a medium brown to dark-brown color
	an earth pigment

earth color (adjective)	umber (adjective)
	of the color of any of various natural brown earth pigments