A man in green and a woman in a gray sweater are looking at some unidentified object.
A man and a woman are looking at the sky.
Sentence two did not state what color shirts the people were wearing and because they are looking at an identified object doesn't mean they are looking at the sky.
exists e1 s1 s2 x1 x2 x3 x4 x5 x6.(at(e1,x6) & n_object(x6) & a_unidentified(s2) & Theme(s2,x6) & Actor(e1,x1) & v_look(e1) & in(x1,x2) & subset_of(x4,x2) & in(x4,x5) & n_sweater(x5) & a_gray(s1) & Theme(s1,x5) & n_woman(x4) & subset_of(x3,x2) & n_green(x3) & n_man(x1))
exists e1 x1 x2 x3 x4.(n_sky(x4) & at(e1,x4) & Actor(e1,x1) & v_look(e1) & subset_of(x3,x1) & n_woman(x3) & subset_of(x2,x1) & n_man(x2))