The musher is pressing the dogs to the finish line.
The dogs of the dog sled are all white and grey.
There is no mention of the color of the dogs.  They might be other colors besides white and grey.
exists e1 x1 x2 x3 x4.(n_line(x3) & of(x3,x4) & n_finish(x4) & n_dog(x2) & n_musher(x1) & to(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_press(e1))
exists e1 p1 x1 x2.(n_dog(x2) & n_dog(x1) & exists s1 s2 x3.(a_all(s2) & Manner(s1,s2) & Theme(s1,x3) & a_white(s1) & n_grey(x3)) & Topic(e1,p1) & Actor(e1,x1) & v_sled(e1) & of(x1,x2))