Give an example of a graph that contains at least 6 vertices, and each vertex has at least 4 neighbors, and the graph has a valid vertex coloring using only 2 colors.
I believe this bipartite graph will do.
Connect 8 vertices, 4 on each side. Each vertex is connected to vertices on the other side.
This should be the simplest possible answer, with 8 vertices total and 4 neighbors each.
9 vertices, some vertices has 5 neighbors, and 2 colors (B: Blue) & (R: Red)