Man and women standing under a red umbrella.
The two woman stood under the black umbrella.
It is unclear what the genders of the two people are(man and woman or two women) and what color umbrella they are standing under (red or black).
Either a man and woman are standing under a red umbrella, or two women are standing under a black umbrella; both cannot be happening simultaneously given the same subjects.
If there is a man and woman, there cannot be two women.