Unfortunately there's not. Like Windows Blinds, Aero is based on bitmap graphic skins. The only way to change the style is to use another theme from another provider, like Window Blinds. You might try keeping Aero on but turning off the transparency in the color options. Then you can change the intensity and be able to better see the active application.
Picture: http://skeene.net/answers/Sharp%20Colors.png
It's easier to see that Explorer is active because it's taskbar button is bright white.
Uninstalled it almost immediately.