Putting color on a wall is at least somewhat artificial, as we found out earlier. Hence it may pay to investigate what walls with true colors could be made of. This way we encounter glass as being a special form of wall. Usually it's just a window which doesn't do much color for a wall -- our brain tells us that all the things "in the window" are actually "behind that opening in the wall". But once the glass becomes less transparent, our brain has a hard time to tell what's going on. Color appears to be on the wall, with single objects behind the wall integrating into the wall -- depending on the optical quality of the transparent part of the glass.
Limit #11 Transparency Looking Like Walls
Which leads to an interesting assumption, again: translucency doesn't necessarily mean clarity, nor truth, nor objectivity. Transparency can as well be a wall, and if used properly, the observer will be just overwhelmed by its beauty not recognizing he's been fooled, again.