There are a number of reasons why I present the 'same' painting in different colours, sepia, monochrome, etc
Here are a few of them -
1) it makes one realize that changing the colour/s of a painting, the painting appears to be different;
2) one becomes aware of things, eg forms, composition, etc, that one was not aware of when perceiving the painting in just one 'set' of colours;
3) that the viewer should apply this experiment and its effects to the work of other artists and other works of art. Imagine for example when a certain van Gogh, Klee, Picasso, Kandinsky, Miro, el Greco, Raphael, etc, etc is presented in a different set of colours... Imagine perceiving things we encounter everyday are perceived in a different 'set' of colours, tones, etc - a sunrise, sunset, a friend, your parents, your dog or cat, your house, room, bread, car, scrambled eggs (for example as blue, red, green, black etc).
4) The variations in colour, tone, etc are endless, as are the consequences and implications of changing the colours of a certain thing.