Sidewinders are not aboreal...the discription is a slender red aboreal snake with horns. Where are these horns on the head and how many were there? I can't think of anything that fits the discription. Are we talking really red or just a reddish tint? I don't suppose it had a rounded snout? Was there a pattern ot it or just a flat colour? Was the head wider than the neck?
I can't think of any red treesnake with horns.