A color which would be 'dirty' if it were the color of a wall, needn't be so in a painting.
We regard the photograph, the picture on our wall, as the object itself (the man, landscape, and so on) depicted there. This need not have been so. We could easily imagine people who did not have this relation to such pictures. Who, for example, would be repelled by photographs, because a face without color and even perhaps a face in reduced proportions struck them as inhuman.
Imagine someone pointing to a place in the iris of a Rembrandt eye and saying, 'The walls of my room should be painted this color.
