There are CSS classes that are built-in to the UI Manager plugin that will allow you to customize the text color and background color of menu items.
kpui-bg-colorname - Changes the background color. ‘colorname’ can be any CSS color as listed here: http://thenewcode.com/1111/Using-CSS-Color-Keywords
kpui-color-colorname - Changes the text color. ‘colorname’ can be any CSS color as listed here: http://thenewcode.com/1111/Using-CSS-Color-Keywords