Needs["Graphics`ArgColors`"] ; a = 0.04; b = 0.003; c = 0.0015; i0 = 0.06; Plot3D[{Abs[(v (a - v) (v - 1) - w + i0 + (b v - c w)I)], ArgColor[(v (a - v) \ (v - 1) - w + i0 + (b v - c w)I)]}, {v, -0.5, 1.2}, {w, -0.1, 0.3}, ImageSize -> {400, 300}, AxesLabel -> {"v", "w", "|v'+i w'|"}]