Actually, you could have gotten both units into pursuit. had you moved the Green unit first.
3b). "no stands can pursue by moving directly forward" - take stand that is closest to the retreating unit and move it center to center against the of closest accessible edge of the closest enemy stand.
Closest accessible edge for the Green unit would be the flank of the remaning stand. To the front of the retreating unit, there are only 3cm. So a cavalry stand could not fit in to the front. You even could bring the light-blue unit into combat (even if there were 4 cm, the gap rule wouldn't let you get all the way there.).
Then, one stand of the blue unit could then pursue directly forward and you could get the pink unit into combat (not mandatory).