For 1, you also have to pass your colours and contour edges to SetContour and SetPalette; you can search for examples in this forum, e.g. Search results for 'user defined palette' - ROOT Forum
like this one: Set User defined Palette of 2D histogram - #4 by OSchaile
Not sure what you mean in the second question; what kind of “polygonal data”? and what kind of “chart”?