In the postscript output files, the shading or color of a specific arc is a weighted average of the prespecified shading or color of the arc types. The weights for each arc type depend on the arc type's proportional contribution to the total probability of an arc. The sequence that appears second will be drawn along the vertical axis. For black and white postscript output, I usually make slow southeastern arcs black and all other arcs gray. For color postscript output, I usually color slow southeastern arcs blue, fast southeastern arcs red, and all other arcs green.
Intermediate values are different shades of grey.