New blog post about color schemes

blog/_posts/2024-10-08-new-color-schemes.md

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+---
+title: "New color schemes"
+layout: archive
+author: Olivier Couet
+---
+
+Choosing an appropriate color scheme is essential for making results easy to understand and
+interpret. Factors like colorblindness and converting colors to grayscale for publications
+can impact accessibility. Furthermore, results should be aesthetically pleasing. The following
+three color schemes, recommended by M. Petroff in [arXiv:2107.02270v2](https://arxiv.org/pdf/2107.02270)
+and available on [GitHub](https://github.com/mpetroff/accessible-color-cycles)
+under the MIT License, meet these criteria.
+
+<center>
+   <img src="{{'/assets/images/accessiblecolorschemes.png' | relative_url}}" alt="Accessible color schemes" style="width: 60%" width="1600" height="749" />
+</center>
+
+The following example demonstrates how to use the accessible color schemes (in this case, the one
+with six colors) to represent a THStack. It also shows that the grayscale version is an
+acceptable alternative.
+
+<center>
+   <img src="{{'/assets/images/thstackcolorscheme1.png' | relative_url}}" alt="THStack color schemes 1" style="width: 60%" width="1600" height="749" />
+</center>
+
+<center>
+   <img src="{{'/assets/images/thstackcolorscheme2.png' | relative_url}}" alt="THStack color schemes 2" style="width: 60%" width="1600" height="749" />
+</center>
+
+{% highlight C++ %}
+void thstackcolorscheme()
+{
+   auto c1 = new TCanvas();
+   auto hs = new THStack("hs","Stacked 1D histograms colored using 6-colors scheme");
+
+   // Create six 1-d histograms  and add them in the stack
+   auto h1st = new TH1F("h1st","A",100,-4,4);
+   h1st->FillRandom("gaus",20000);
+   h1st->SetFillColor(kP6Blue);
+   hs->Add(h1st);
+
+   auto h2st = new TH1F("h2st","B",100,-4,4);
+   h2st->FillRandom("gaus",15000);
+   h2st->SetFillColor(kP6Yellow);
+   hs->Add(h2st);
+
+   auto h3st = new TH1F("h3st","C",100,-4,4);
+   h3st->FillRandom("gaus",10000);
+   h3st->SetFillColor(kP6Red);
+   hs->Add(h3st);
+
+   auto h4st = new TH1F("h4st","D",100,-4,4);
+   h4st->FillRandom("gaus",10000);
+   h4st->SetFillColor(kP6Grape);
+   hs->Add(h4st);
+
+   auto h5st = new TH1F("h5st","E",100,-4,4);
+   h5st->FillRandom("gaus",10000);
+   h5st->SetFillColor(kP6Gray);
+   hs->Add(h5st);
+
+   auto h6st = new TH1F("h6st","F",100,-4,4);
+   h6st->FillRandom("gaus",10000);
+   h6st->SetFillColor(kP6Violet);
+   hs->Add(h6st);
+
+   // Draw the stack with colors.
+   hs->Draw();
+   TLegend *l = gPad->BuildLegend(.8,.55,1.,.9,"","F");
+   l->SetLineWidth(0);
+   l->SetFillStyle(0);
+
+   // Draw the stack using gray scale.
+   auto c2 = new TCanvas();
+   c2->SetGrayscale();
+   hs->Draw();
+   l->Draw();
+}
+{% endhighlight %}
+
+These new color schemes, now in the master version of ROOT, will be available
+in version 6.34.