TGraph2D set axes labels

I have a 2D TGraph, with a colour column next to it (see below).

I want to manually choose where to label the ticks, and ideally not with numbers but with letters (s_1, s_2 etc.). The same for the colour chart on the left.
Like in Matlab basically, where I can define the set of tick labels.

Any ideas on how to do this?

You should get the 2D histogram from the TGraph2D and set the labels on it using
root.cern.ch/root/html/TAxis.ht … etBinLabel