You can design the color component of the volume transfer function using the controls in the top of the Volume plot attributes window. The controls are similar to the controls for the Color Table Window. There is a color spectrum that has color control points which determine the final look of the color table. Color control points are added and removed using the "+" and "-" buttons. Dragging control points with the mouse moves them and changes their order. Right-clicking on a color control point displays a popup color menu from which a new control point color can be chosen.