I found this post. Here, it was supposed to use an TNtuple with four entries: x,y,z,val. Then, one draws the tuple with option “col” or “colz” as
ntuple->Draw("x:y:z:val","","COL");
Unfortunately, for me (root version 6.20.00), only the first point of the ntuple is drawn and its fourth component determines its color. If I enter only
ntuple->Draw(“x:y:val”,"","");
then I get a TPolyMarker3D with all points, but they of course all have the same color.