Spectators are seated behind a blue wall.
There is a blue wall behind the spectators.
The blue wall in front isn't necessarily behind the spectators and depends on perspective.
exists e1 s1 x1 x2.(behind(e1,x2) & n_wall(x2) & a_blue(s1) & Theme(s1,x2) & Theme(e1,x1) & v_seat(e1) & n_spectator(x1))
exists p1 x1 x3.(n_spectator(x3) & exists s1 x2.((x1 = x2) & behind(x2,x3) & n_wall(x2) & a_blue(s1) & Theme(s1,x2)))