To change the text of the caption (banner), go to the Menu Look tab in Start Menu settings. Look or search for the setting called "Menu Caption".
To change the background of the caption, you will need to understand the skin format, how the background is drawn using slices and then edit the skin. The skin format is described here:
http://www.classicshell.net/tutorials/skintutorial.html. You will also need to download and install Resource Hacker from
http://www.angusj.com/resourcehacker/ to edit the skin. Next go to C:\Program Files\Classic Shell\Skins in Explorer and copy the skin you want to some other folder, such as the Desktop. (The file extension for classic style is .skin). Now open this skin in Resource Hacker and do the modifications you want, save the skin and copy it back to C:\Program Files\Classic Shell\Skins\. Switch to the new skin from the Skins tab in Settings.
The skin also contains the parameters Caption_font=, Caption_text_color= and Caption_padding= which you can change.