The
compound color components to color function compounds the individual color components (their values being between 0 and 1) to a resulting
color, which will be returned on the output as a numeric value. It is not necessary to enter the alpha component for normal colors; in this case the default value 1 will be used. When setting the alpha component equal 0 the transparent color will be used.
The alpha component determines the color transparency. Its significance is above all in using with the
3D graphics. Its value may range between 0=transparent color and 1=opaque color (default value of the parameter). With graphical operations by setting the alpha component equal 0 (it is not necessary to set other components) the transparent color can be selected (the $FF000000 number after conversion). By setting it equal 0.56 the shadow color will be used (the $70000000 number after conversion).