With vexillum you can change the background color, font color and border color of your notification banners! You can also use cool gradients! <br/><br/>
<img src="http://f.cl.ly/items/2K1U201s0a1J1Y183v3l/Screenshot%202012.01.30%2022.22.41.png" width="130px"/>
<img src="http://f.cl.ly/items/1z3h0z2w3x2b151G2W0c/Screenshot%202012.01.30%2022.23.12.png" width="130px"/><br/><br/>
Simply go in Settings.app->Vexillum and change the color. <b>And all for free! </b><br/><br/>
Check out the video by jailbr3k below.