You can customize the Site Actions menu styling by overriding a few rules from the COREV4.css.
We will customize the menu item hover background, link colors and the menu border color.
The code:
/*site actions hover */
div.ms-MenuUIPopupScreen div.ms-MenuUIPopupInner ul.ms-MenuUIUL div.ms-MenuUIULItemHover {
background-color:#dcdcdc;
border-color:#E0E0E0;
}
/* site actions link color */
div.ms-MenuUIPopupScreen div.ms-MenuUIPopupInner div.ms-MenuUILarge ul.ms-MenuUIUL div.ms-MenuUIULItem a.ms-MenuUIULLink,
div.ms-MenuUIPopupScreen div.ms-MenuUIPopupInner div.ms-MenuUILargeRtL ul.ms-MenuUIUL div.ms-MenuUIULItem a.ms-MenuUIULLink {
color: #28387E !important;
}
div.ms-MenuUIPopupScreen div.ms-MenuUIPopupInner ul.ms-MenuUIUL div.ms-MenuUIULItemHover a.ms-MenuUIULLink {
color:#000 !important;
}
/* menu borders */
.ms-MenuUIPopupBody {
border-color:#E0E0E0 !important;
}
/* menu borders - inner */
div.ms-MenuUIPopupScreen div.ms-MenuUIPopupInner ul.ms-MenuUIUL {
border-color:#f8f8f8 !important;
}
After implementing the code above: