Yes, this is possible using the drawing option "lego2".
The example below illustrates how to define your own color palette.
There is a default palette defined with 50 colors.
The example shows how to define non-equidistant contour levels.
{
gROOT->Reset();
TFile f("hsimple.root");
Int_t colors[10]={10,10,2,3,4,5,6,7,8,9};
float levels[10]={0,1,10,60,200,300,400,500,600,700};
//the color corresponding to the minimum is the FillColor +1;
hpxpy->SetFillColor(4);
hpxpy->SetContour(4,levels);
gStyle->SetPalette(10,colors);
hpxpy->Draw("lego2");
gStyle->SetPalette(); //back to default palette
}
Rene Brun