The "PFC" draw option for THStack objects is broken by prior calls to the GetMaximum() method, i.e., the stack is rendered unfilled instead of being automatically colorized.
Oddly enough, if the "nostack" option is added to the draw options, the correct behaviour is seen (automatically colorized hist).
MWE: see attached thstackpalettecolor.C
Buggy behaviour: see attached thstack_pfc_bug.pdf
If I comment-out the call to GetMaximum, I get thstack_pfc_correct.pdf