Slide Menu has StyleFolder property to easily change styles with only one line of code.

For example:
    osm.StyleFolder = "/slidemenu/styles/xp_blue";
    osm.StyleFolder = "/slidemenu/styles/pro_5";


Below are exactly the same menus with only StyleFolder property set to different styles.    
Download Slide Menu with all examples and styles

StyleFolder = "/slidemenu/styles/pro_2" Parent 1 Child 1 Child 2 Child 3 Child 4 Parent 2 Child 1 Child 2 Child 3 Child 4 Parent 3 Child 1 Child 2 Child 3 Child 4

StyleFolder = "/slidemenu/styles/pro_7" Parent 1 Child 1 Child 2 Child 3 Child 4 Parent 2 Child 1 Child 2 Child 3 Child 4 Parent 3 Child 1 Child 2 Child 3 Child 4

StyleFolder = "/slidemenu/styles/pro_8" Parent 1 Child 1 Child 2 Child 3 Child 4 Parent 2 Child 1 Child 2 Child 3 Child 4 Parent 3 Child 1 Child 2 Child 3 Child 4

<osm:SlideMenu runat="server"
        id="tutStyles"
        StyleFolder = "/slidemenu/styles/pro_2"
        SelectedId = c13 >
    <menuitems>
        <osm:Parent id="p1">Parent 1</osm:Parent>
            <osm:Child id="c11">Child 1</osm:Child>
            <osm:Child id="c12">Child 2</osm:Child>
            <osm:Child id="c13">Child 3</osm:Child>
            <osm:Child id="c14">Child 4</osm:Child>
        <osm:Parent id="p2">Parent 2</osm:Parent>
            <osm:Child id="c21">Child 1</osm:Child>
            <osm:Child id="c22">Child 2</osm:Child>
            <osm:Child id="c23">Child 3</osm:Child>
            <osm:Child id="c24">Child 4</osm:Child>
    </menuitems>
</osm:SlideMenu>