In the book Remarks on Colors, Wittgenstein has claimed that transparent white objects do not and cannot exist, and that they cannot even be imagined. He had also claimed that luminous gray does not exist and cannot even be conceived. However, his arguments which aim to identify contradictory features of hypothetical transparent white media rely on incorrect assumptions about their properties and effects. Furthermore, some real objects and atmospheric phenomena can have features of transparent white media. As concrete examples of (...) Wittgenstein's 'impossible' colors, this paper contains two simple computer-generated graphical displays, one depicting a scene that includes a transparent white sheet, and another which conveys the impression of luminous gray. (shrink)