Here is an example of my use case: I have four detector elements, whose current state I need to depict as a 2x2 2D plot. Five colours must roughly represent the values.

```
Red: 2<v
Orange: 1<v<2
Green: v<1
Green: -1<v
Azure: -2<v<-1
Blue: v<-2
```

The following code works as desired ONLY if at least one value gets into the “positive saturation” range, i.e. Red:2<v:

```
{
Int_t colors[6];
colors[5] = kRed +2;
colors[4] = kOrange+2;
colors[3] = kGreen +2;
colors[2] = kGreen +2;
colors[1] = kAzure +2;
colors[0] = kBlue+2;
gStyle->SetPalette(6, colors);
gStyle->SetNumberContours(6);
TCanvas* c = new TCanvas("c", "c", 400, 400);
TH2F* h = new TH2F("h", "h", 2, 0, 2, 2, 0, 2);
h->SetStats(kFALSE);
h->SetMaximum( 3.);
h->SetMinimum(-3.);
h->SetBinContent(1, 1, 2.5);
h->SetBinContent(1, 2, 0.5);
h->SetBinContent(2, 1, -0.5);
h->SetBinContent(2, 2, -1.5);
h->Draw("COLZ2");
}
```

Otherwise, the desired functionality breaks, and some sort of interpolation comes into play. The following variations demonstrate that:

```
h->SetBinContent(1, 1, 1.5);
h->SetBinContent(1, 2, 0.5);
h->SetBinContent(2, 1, -0.5);
h->SetBinContent(2, 2, -1.5);
h->Draw("COLZ2");
h->SetBinContent(1, 1, 1.5);
h->SetBinContent(1, 2, 0.5);
h->SetBinContent(2, 1, -0.5);
h->SetBinContent(2, 2, -2.5);
h->Draw("COLZ2");
```

How can I avoid that?

Thanks!