code: def modify_colorpoint(self, n, position=0.5, color1=[1.0,1.0,1.0], color2=[1.0,1.0,1.0]):
          
          if    n==0.0                         : position = 0.0
          elif  n==len(self._colorpoint_list)-1: position = 1.0
          else: position = max(self._colorpoint_list[n-1][0], position)
  
          self._colorpoint_list[n] = [position, color1, color2]
          self.update_image()
          self.save_colormap("Last Used")
docs: Changes the values of an existing colorpoint, then updates the colormap.