When using the “COL” option to draw a 2D histogram, the empty bins show up as the
color white, even when I extend the color palette axis down to -10. I used these commands
to draw a 2D histogram called “hxy”:
root  gStyle->SetPalette(1,0)
root  hxy->SetMinimum(-10)
root  hxy->Draw(“COLZ”)
and everything looks okay except the empty bins are white instead of the blue color
indicated on the color palette axis at the number 0 (I have attached the plot). How can I fix this?