Tracy, you could achieve this by overwriting the css property of the pop up title bar color. One way to do that is to figure out which id or class defines the current color, and then overwrite that property.
For example, if you add:
.esriPopupMobile .titlePane{background: none repeat scroll 0 0 red !important;}
at the end of the file jimu.js/css/dojo-override.css then the mobile popup title pane element will be red. I would use something like Google Chrome Developer tools to figure out which css classes you need to change. Hope this points you in the right direction.