LEGO2 behavior

ROOT
1

Under what circumstances does LEGO2 produce colored plots? I have a bunch of different histograms some of which come out as expected (i.e in color) and the others are just plain black with the actual structure barely visible. Can I know what I am missing?

c1->cd(1);
eta->Draw("LEGO2");
//  ... other plots
c2->cd(1);
phi->Draw("LEGO2");

eta comes out in all balck, while phi is normal.

2

Always.
See root.cern.ch/root/html/THistPainter.html#HP17
Send a small macro reproducing what you see to get further help.