I think you need to specify your ROOT version (I’m afraid I see no such problem with my ROOT 5.34/26).
I tried: {
gROOT->SetStyle("Pub");
// gROOT->ForceStyle(1); // uncomment either this line ...
TCanvas *c = new TCanvas("c", "c");
// the "hsimple.root" file comes from ${ROOTSYS}/tutorials/
TFile *f = TFile::Open("hsimple.root");
TH2F *hpxpy; f->GetObject("hpxpy", hpxpy);
// hpxpy->UseCurrentStyle(); // ... or this line
hpxpy->Draw("colz");
}