Anyone running the Aero Glass theme in Windows Vista has the option of choosing between multiple color schemes: default, graphite, blue, teal, red, orange, pink, or frost. The color scheme you choose, however, does not affect the color of your Taskbar.
I was just looking through a Neowin post from someone who actually did something pretty clever to get around the limitation. If you have Aero enabled in Vista then that means your taskbar is transparent and you can see through it and onto your desktop’s background. So what he decided to do is modify the bottom portion of his background to make the Taskbar appear to be a different color.
As you can see in the screenshot above he chose to do a rainbow gradient on the background so that all of the colors flowed together quite nicely. I don’t think I’ll be doing a rainbow effect like he did, but this is quite a clever “hack” to make the Taskbar any color that you would like it to be.
If you’re looking for a free program that will let you apply similar gradient effects (which make the colors blend nicely together) then you should checkout Paint.NET. It doesn’t cost a thing and with a little bit of work you should be able to get the exact look that you want.