huey: Internal maintenance specification

# - - -   M e n u B a r . _ _ h e l p R G B

    def __helpRGB ( self ):
        """Help for the RGB color model.
        """
        self.__dialog ( 'Help: The RGB color model',
            "In the RGB color model, color is specified by three "
            "parameters: red, green, and blue.  These are called the "
            "'additive primary colors;' if you drag all three "
            "sliders all the way up, you get white.  RGB color mixing "
            "is used in display screens and also in stage lighting." )