Princeton's WordNet

1. red, redness(noun)

   red color or pigment; the chromatic color resembling the hue of blood

   Synonyms:
   red, red ink, inflammation, bolshy, bolshie, loss, rubor, redness

   Antonyms:
   neutral, uncolored, uncoloured, bloodless, achromatic

2. Red, Red River(noun)

   a tributary of the Mississippi River that flows eastward from Texas along the southern boundary of Oklahoma and through Louisiana

   Synonyms:
   red ink, bolshie, loss, redness, bolshy

   Antonyms:
   achromatic, bloodless, neutral, uncolored, uncoloured

3. Bolshevik, Marxist, red, bolshie, bolshy(noun)

   emotionally charged terms used to refer to extreme radicals or revolutionaries

   Synonyms:
   red ink, bolshie, red, loss, redness, bolshy

   Antonyms:
   uncoloured, uncolored, achromatic, neutral, bloodless

4. loss, red ink, red(adj)

   the amount by which the cost of a business exceeds its revenue

   Synonyms:
   passing, red, exit, deprivation, release, red ink, going, bolshy, personnel casualty, expiration, loss, redness, departure, bolshie

   Antonyms:
   achromatic, uncoloured, neutral, uncolored, bloodless

5. red, reddish, ruddy, blood-red, carmine, cerise, cherry, cherry-red, crimson, ruby, ruby-red, scarlet(adj)

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

   Synonyms:
   ruby, sanguine, rubicund, flushed, cherry-red, scarlet, reddish, red-faced, violent, red, blood-red, reddened, florid, carmine, ruddy, crimson, cherry, cerise, ruby-red

   Antonyms:
   bloodless, neutral, uncoloured, uncolored, achromatic

6. crimson, red, violent(adj)

   characterized by violence or bloodshed

   Synonyms:
   ruby, wild, fierce, cherry-red, scarlet, reddish, red-faced, tearing, violent, flushed, blood-red, reddened, trigger-happy, carmine, vehement, cerise, ruddy, crimson, cherry, red, ruby-red

   Antonyms:
   achromatic, uncolored, uncoloured, bloodless, neutral

7. crimson, red, reddened, red-faced, flushed(adj)

   (especially of the face) reddened or suffused with or as if with blood from emotion or exertion

   Synonyms:
   ruby, rosy, ablaze(p), blushing(a), cherry-red, scarlet, reddish, red-faced, violent, flushed, blood-red, reddened, inflamed, carmine, cerise, rose-cheeked, ruddy, crimson, cherry, blushful, red, ruby-red, rosy-cheeked

   Antonyms:
   bloodless, achromatic, neutral, uncolored, uncoloured