A man in a helmet is riding a bike.
A man in a red helment is riding a bike.
A man doesn't have to wear a red helmet, it could be any color.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_ride(e1) & n_bike(x3) & in(x1,x2) & n_helmet(x2) & n_man(x1))
exists e1 s1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_ride(e1) & n_bike(x3) & in(x1,x2) & n_helment(x2) & a_red(s1) & Theme(s1,x2) & n_man(x1))