olive-drab uniform vs olive drab

olive-drab uniform and olive drab both are nouns.

Word	Noun	Adjective	Verb	Adverb
olive-drab uniform	Yes	No	No	No
olive drab	Yes	No	No	No

As nouns, olive-drab uniform and olive drab are synonyms defined as:

olive-drab uniform and olive drab: military uniform of the United States Army; made from cloth of a dull olive color

olive-drab uniform (noun)	olive drab (noun)
military uniform of the United States Army; made from cloth of a dull olive color	a cloth of an olive-brown color used for military uniforms
	military uniform of the United States Army; made from cloth of a dull olive color
	a dull greyish to yellowish or light olive brown