struct MyDisplay : public Display {
  virtual void MyDisplay::Paint(Draw& w,const Rect& r,
                                const Value& q,Color ink,
                                Color paper,dword style) const
  {
    w.DrawRect(r, paper);
    w.DrawText(r.left, r.top, text, StdFont(), Blue()); // <- the color I want goes in here
  }
};

...

TreeCtrl tree;
tree.SetDisplay(Single<MyDisplay>());

...