Allow opacity change for 25d renderer colors (fix #14877)

(cherry-picked from 7af95b1)

src/gui/symbology-ng/qgs25drendererwidget.cpp

@@ -38,6 +38,16 @@ Qgs25DRendererWidget::Qgs25DRendererWidget( QgsVectorLayer* layer, QgsStyleV2* s
 
   setupUi( this );
 
+  mWallColorButton->setColorDialogTitle( tr( "Select wall color" ) );
+  mWallColorButton->setAllowAlpha( true );
+  mWallColorButton->setContext( "symbology" );
+  mRoofColorButton->setColorDialogTitle( tr( "Select roof color" ) );
+  mRoofColorButton->setAllowAlpha( true );
+  mRoofColorButton->setContext( "symbology" );
+  mShadowColorButton->setColorDialogTitle( tr( "Select shadow color" ) );
+  mShadowColorButton->setAllowAlpha( true );
+  mShadowColorButton->setContext( "symbology" );
+
   if ( renderer )
   {
     mRenderer = Qgs25DRenderer::convertFromRenderer( renderer );