The graph to the right represents a map of the states California, Nevada, Utah, Colorado, and Kansas. Two vertices are joined by an edge if and only if the states share a stretch of common border. Find the smallest number of colors that can be used to color the map so that any two states sharing a stretch of common border are not colored with the same color. CA UT KS The smallest number of colors that can be used to color the map whose graph is shown is (Type a whole number.) NV CO 8