From an accessibility point of view there are many people who find it easier to control their computers by (effectively) the keyboard, rather than the mouse. One of the things that comes up semi-regularly is mistakes caused by not realising which window is the active one.
I'm looking for a tweak or even a program that makes it easier to see which window is the active one in OSX. I'd like like something that just, for example, dramatically increased the shadow, or boardered the active window in Red.