One guy and one girl painting a colorful picture on the road.
They are outside.
The road is outside. A guy and a girl is two people, therefore the pronoun "they" is used, to describe two people.
exists s1 x1 x5.(n_road(x5) & a_topic(s1) & all s2 x2.((n_picture(x2) & a_colorful(s2) & Theme(s2,x2)) -> exists x3 x4.(subset_of(x3,s1) & on(x3,x5) & for(x3,x2) & n_painting(x3) & of(x3,x4) & n_girl(x4) & card_eq_1(x3))) & subset_of(x1,s1) & n_guy(x1) & card_eq_1(x1))
exists s1 x1.(n_thing(x1) & Theme(s1,x1) & a_outside(s1))