grim vs drab

grim is not a noun while drab is a noun.

Word	Noun	Adjective	Verb	Adverb
grim	No	Yes	No	No
drab	Yes	Yes	No	No

As adjectives, grim and drab are synonyms defined as:

Other synonyms of grim include blue, dark, dingy, disconsolate, dismal, drear, dreary, gloomy, sorry.

grim (noun)	drab (noun)
	a dull greyish to yellowish or light olive brown

grim (adjective)	drab (adjective)
shockingly repellent; inspiring horror	of a light brownish green color
filled with melancholy and despondency	lacking brightness or color; dull
causing dejection	causing dejection
not to be placated or appeased or moved by entreaty	lacking in liveliness or charm or surprise
harshly ironic or sinister
harshly uninviting or formidable in manner or appearance