red-green color blindness

NOUN
25 LETTERS · STARTS WITH R

red-green color blindness is a valid 25-letter word worth 29 points in Scrabble and 37 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
R1E1D2-0G2R1E1E1N1C3O1L1O1R1B3L1I1N1D2N1E1S1S1
1 + 1 + 2 + 0 + 2 + 1 + 1 + 1 + 1 + 0 + 3 + 1 + 1 + 1 + 1 + 0 + 3 + 1 + 1 + 1 + 2 + 1 + 1 + 1 + 1 =29 PTS
DOUBLE WORD → 58TRIPLE WORD → 87
MEANING

What does red-green color blindness mean?