Children are learning about a firetruck.
Children are learning about a purple firetruck
The color of the fire truck is not stated, so it cannot be inferred that the fire truck is purple.
exists e1 x1 x2.(about(e1,x2) & n_firetruck(x2) & Actor(e1,x1) & v_learn(e1) & n_child(x1))
exists e1 x1 x2 x3.(about(e1,x2) & n_firetruck(x2) & of(x2,x3) & n_purple(x3) & Actor(e1,x1) & v_learn(e1) & n_child(x1))