Making background windows less obvious

Lately I’ve been spending a lot of time with my entire screen covered by MacVim and Terminal windows. As you can see, I use the same "legal pad yellow" background color for both because I find it much easier on my eyes.

The problem is that all these windows look the same, and it is hard to tell which one is frontmost without looking at the title bar. While it may seem fairly easy to distinguish the windows in the sample screenshot, it becomes much harder when the entire 27" display is just a screenful of black text swimming in a sea of yellow. The distance between the titlebar and the bottom of the window (where your eyes are often focussed, especially in the case of Terminal windows) can easily be around 12".

With the constant Command-Tabbing back and forth among applications, I find myself typing into the wrong application probably dozens of times a day.

I’m wondering if there’s something out there that could be used to make the frontmost application windows stand out a little more, for example, having background application windows become subtly transparent or darker. I’ve done a brief Google, but haven’t found anything yet.

And note, in general I think that for most applications Apple’s UI does a fine job of making the frontmost application stand out. The problem is unique to my incredibly similar Terminal and Vim windows with their identical yellow backgrounds and black fonts. I’ve turned on the blinking cursor in the Terminal, and switched off the "Graphite" appearance in the system preferences, but its just not enough.

Suggestions are welcome.