diff --git a/docs/doxygen/overviews/commondialogs.h b/docs/doxygen/overviews/commondialogs.h
index bd05480a1d..4cdf52abd2 100644
--- a/docs/doxygen/overviews/commondialogs.h
+++ b/docs/doxygen/overviews/commondialogs.h
@@ -48,11 +48,11 @@ controls to select a precise colour, and add it to the custom colour palette.
 
 Under non-MS Windows platforms, the colour selector is a simulation of most of
 the features of the MS Windows selector. Two palettes of 48 standard and 16
-custom colours are presented, with the right-hand area containing three sliders
-for the user to select a colour from red, green and blue components. This
+custom colours are presented, with the right-hand area containing three or four sliders
+for the user to select a colour from red, green, blue and opacity (optionally) components. This
 colour may be added to the custom colour palette, and will replace either the
 currently selected custom colour, or the first one in the palette if none is
-selected. The RGB colour sliders are not optional in the generic colour
+selected. The RGB or ARGB colour sliders are not optional in the generic colour
 selector. The generic colour selector is also available under MS Windows; use
 the name wxGenericColourDialog.