Attempt to solve T41708,

Refresh always when clicking on a palette color (state here may be same
as state of button, not causing a refresh as it should)

source/blender/editors/interface/interface_handlers.c

@@ -4334,6 +4334,9 @@ static int ui_do_but_COLOR(bContext *C, uiBut *but, uiHandleButtonData *data, co
 				PaletteColor *color = but->rnapoin.data;
 				palette->active_color = BLI_findindex(&palette->colors, color);
 				
+				/* enforce redraw, sometimes state here can already be exit */
+				ED_region_tag_redraw(data->region);
+
 				if (!event->ctrl) {
 					float color[3];
 					Scene *scene = CTX_data_scene(C);