The coloring the vertices of a graph is one of the fundamental concepts of graph theory. It is widely believed that coloring was first mentioned in 1852 when Francis Guthrie asked if four colors are enough to color any geographic map in such a way that no two countries sharing a common border would have the same color. If we denote the countries by points in the plane and connect each pair of points that correspond to two countries with a common border by a curve, we obtain a planar graph. The celebrated four color problem asks if every planer graph can be colored with 4 colors. The four...