Calling this function brings up the modal "Select Color" dialog, allowing the user to select a color from the default color list, or add a color to the custom color list.
The parameter passed in default color is an atom representing the default color to select, in #RRGGBB format. Passing -1 specifies that the color black (#000000) is the default color.
Example:
-- get a color; red ( #FF0000 ) is the default atom color color = getColorDialog( Window, #FF0000 )