You can override the menu styles like this (add this to your page)

<style type="text/css">

                                .RS_ContextMenuItem

                                {

                                    text-align: left !important;

                                }

                                .RS_ContextMenuTable

                                {

                                    background-image:none !important;

                                }

                                .RS_ContextMenuItem_Over {

                                                background:                       #00F0BC !important;

                                                border:                                 1px solid #FF2D96 !important;

                                }

</style>

First one asserts the align, second one removes the gradient and third affects the highlight colors.  There are other options, use the IE8 debugger (F12) to investigate the styles, or email support at keyoti.com