Writing the possible results that meet the requirements, we have:
(red dice result, green dice result)
(1,6), (2,5) , (2,6) , (3,4), (3,5) , (3,6) , (4,3), (4,4) , (4,5) , (4,6), (5,2), (5,3), (5,4), (5,5), (5,6), (6,1),(6,2), (6,3), (6,4), (6,5), (6,6)
The answer is 21 possible options.