When you double-click a colormap module the window shown below opens. The data range may be set by typing into the text fields shown near the ends of the color bar (defaults are 0 and 100). If the first input tab of a colormap module is connected to a module output the the data range will be automatically set to the min and max of the data component of the output.

Each of the Hue, Saturation, Value and Opacity regions defaults to two control points. You can drag the control points by clicking on them. Double-clicking elsewhere in the control regions creates new control points.