A man in a red shirt and blue jeans is standing in front of a wall with other people's shadows in front of him on the pavement.
A man stands by a wall.
man in a red shirt and blue jeans is standing in front of a wall is rephrased as man standing by a wall.
a man can wear a red shirt and blue jeans, a man can stand in front of a wall which also means that he is "by" the wall
A man wearing clothes near a wall is a subset of a man near a wall.