Random processes and Visual perception.
After Dr. E Porteus demonstration: “The shortest route problem in optimisation models” - Fondations of stochastic inventory theory - Stanford University Press. 2002.

Our algorithmic method  has been given in three steps. The first two steps are the maximal mono-chromatic and then maximal di-chromatic coloring of the faces in such a way that the resulting uncolored (white) regions of the incomplete two-colored map induce no odd-cycles so that in the (final) third step four coloring of the map has been obtained almost trivially. In order to make the map-coloring algorithm more visible and meaningful let us define the four-color set as 

C = {B,G, dB, lB}, where

As a constructional engineer, born in 1944, I am self-taught in mathematics and art. I created these pictures using the SURFER-program.