B-chromatic number 4 Chromatic number 4 Color 4 Coloring 4 Graph G 4 Graph theory 4 Graphic methods 4 Induced subgraphs 4 Monotonicity 4 P4-tidy graphs 4 Polynomial approximation 4 Polynomial-time algorithms 4 b-coloring 4 b-continuity 4 b-monotonicity 4 B-coloring 2 B-continuity 2 B-monotonicity 2 Cographs 2 P 4-sparse graphs 2