(* Contour plot of the hyperbolic paraboloid x^2 - y^2 modulated
   by Cos[x^4 y^4]; contours are color coded with Hue[].      *)

ContourPlot[
  Cos[x^4 y^4 ] (x^2 - y^2), {x, -3, 3}, {y, -3, 3}, 
    Contours -> 100, PlotPoints -> 300, 
    ContourLines -> False, Frame -> False,
    ColorFunction -> Hue];