red vs ruby

red and ruby both are nouns.

Word	Noun	Adjective	Verb	Adverb
red	Yes	Yes	No	No
ruby	Yes	Yes	No	No

As adjectives, red and ruby are synonyms defined as:

red and ruby: of a color at the end of the color spectrum (next to orange); resembling the color of blood or cherries or tomatoes or rubies

Other synonyms of red include blood-red, carmine, cerise, cherry-red, cherry, crimson, reddish, ruby-red, ruddy, scarlet.

As nouns, ruby is a hyponym of red; that is, ruby is a word with a more specific, narrower meaning than red:

red (noun)	ruby (noun)
red color or pigment; the chromatic color resembling the hue of blood	a deep and vivid red color
emotionally charged terms used to refer to extreme radicals or revolutionaries	a transparent piece of ruby that has been cut and polished and is valued as a precious gem
the amount by which the cost of a business exceeds its revenue	a transparent deep red variety of corundum; used as a gemstone and in lasers

red (adjective)	ruby (adjective)
(especially of the face) reddened or suffused with or as if with blood from emotion or exertion	of a color at the end of the color spectrum (next to orange); resembling the color of blood or cherries or tomatoes or rubies
of a color at the end of the color spectrum (next to orange); resembling the color of blood or cherries or tomatoes or rubies
characterized by violence or bloodshed