Visual Studio 2010 Themes : Properties Reference

I would like to change the color of the vertical line of collapse/expand code. Cannot manage to find the right property in the "Customize Colors" Dialog in the Themes Menu.

I did not manage to find anywhere a decent, exhaustive, and ideally visual reference for the theme properties. I usually end-up trying blindly and changing obscurely named properties on and on, until I finally stumble on the right property by chance, or give up.

this May also be hidden somewhere in Environment>Fonts and Colors...

Any 开发者_运维百科Ideas ?