Hi.
Mostly, there is no title bar in the skins provided by WD. It's just a section in the upper side of an image. Perhaps you can search your project directory in order to find the background image used for your skin, and edit that bitmap to change the color you say.
I don't have WD 24 but in the Description of any window should be the "property" pointing to the image you need to modify.
Regards.