In AGD Interactive's King's Quest III Redux, Alexander is portrayed wearing a torn purple tunic and blue tights with black boots. This outfit seems to be an amalgamation of his clothing in both the King's Quest III box art and game sprite.
In IA's King's Quest III Gold Edition, he is shown to be wearing blue trousers and a long, blue-sleeved tunic topped by an over-tunic that is brown around the shoulders and green below, probably as an homage to his canonical King's Quest 6 outfit. He also wears a fine blue outfit befitting a prince in the ending.
In The Silver Lining, he is seen with an elegant green tunic with gold embroidery and a high collar worn over green trousers, topped with a flowing red cape. His hair is cut much shorter, in a spiky style.