Oh wow! Very nice.
I was imaging that one just last night as well.
For a quick fix you can invert the pic get rid of the green halos, reinvert and apply as a color layer with a 80% blend to get your stars less purple.
But the way to do it is to shoot a lot more Sii and Oiii then balance the background ADU to match the green Ha. You'll then get nice NB star colors.