Navigation bar animation problem

i have a problem with smooth animation of my navigation bar.

There is this “Red” Part, which i want to make transparent. So that when you click on “Home” or “News” or etc. the Blue Bubble together with this “Red” Part moves to the direction of the chosen Title.
I need the “Red” Part to be transparent so that it doesn’t look bad on the background picture while the SmartAnimate runs.

I tried to subtract the “Red” Part with the Blue Rectangle of the navigation bar - and it worked but only wlihe being static, not during the animation itself. (which is the problem)