do the glColor call in compat mode when index is set in the state.

this is not necessary in core profiles since shader based rendering is
used, which does not rely on glColor

libs_required/ACG/GL/ColorStack.cc

@@ -242,7 +242,8 @@ bool ColorStack::Node::setIndex (size_t _idx) const
 {
   if (colorStartIdx_ && colorStartIdx_ + _idx < colorEndIdx_)
   {
-    //glColor(translator_->index2color(colorStartIdx_ + _idx));
+    if(ACG::compatibilityProfile())                               //only change glColor in compat mode as shader pipeline 
+      glColor(translator_->index2color(colorStartIdx_ + _idx));   //renderer on core profiles does not rely on glColor
     return true;
   }
   return false;