Hello,
That would require custom CSS changes which we do not provide support for these types of modifications. I would suggest using Firebug to help you identify any CSS you need to change.
http://www.shape5.com/joomla_tutorials.htmlHere is an example of how you could add a hover effect to the sub menu text:
.S5_submenu_item a :hover {
color: #ff0000 !important;}
.S5_submenu_item :hover {
color: #ff0000 !important;}
-Mike