@ricardor,
Did you down load the script I attached, then right click and run? Did is work?
Note when you click on the Legend for a specific Overlay group ( in my example C1, or C2, C3, C4) it colors and patterns for both Y variables.
Instead double click on the Legend, select each Legend items and change accordingly. i do not have a Mac to test if there is a differenc by OS.
However, if teh script I had attached runs, then you know it is doable,