I have to apologize in advance for the (likely) case the answer to this question is trivial or given already. I just didn’t find it.
I am drawing a TH2D with the “COLZ” option and the “fancy” palette (gStyle->SetPalette(1)). The range of the color scale is adjusted with histo->SetMaximum / SetMinimum.
Any bin with contents greater than the scale’s maximum is drawn in red, which means “overflow - out of range”. This is perfect. But bins with contents smaller than the scale’s minimum are set to the frame fill color, as if they were empty. How do I get them drawn in dark blue, meaning “underflow but greater than zero”? Setting gStyle->FrameFillColor to blue is not possible as “nothing at all” and “something but below range” does make a great difference for me. I need a real marker for “just below range”.
PPS: Using ROOT 5.08/00.