If you like the idea of having multi-colored taskbar buttons, you might want to check out TaskBowFree. TaskBow Free is a taskbar replacement for Windows 7, Windows Vista, Windows XP and Windows 2000.
Once installed, TaskBow assigns colors automatically to your taskbar buttons, although they can be configured to your liking. If you exit the app, your taskbar will return to normal default.
When you first start TaskBowFree, it has several default appointment colors for applications that are commonly used, for instance, Microsoft Word, Notepad, Excel, Outlook, etc.
TaskBowFree also allows you to collect and organize programs in the taskbar, organize the Quick Launch buttons and add a special menu to the taskbar right-click.
TaskBow is a less-than 1 MB download and you can get it here.