When ::use-alpha is %TRUE, colors may have alpha (translucency) information. When it is %FALSE, the #GdkRGBA struct obtained via the #GtkColorChooser:rgba property will be forced to have alpha == 1.
Implementations are expected to show alpha by rendering the color over a non-uniform background (like a checkerboard pattern).
The ::rgba property contains the currently selected color, as a #GdkRGBA struct. The property can be set to change the current selection programmatically.