Hi there,
To change the slider you have to disable the slider first from the page meta option & then use any of your choosen slider plugin like revolution slider or layer slider to make your video slider & use it in the vc option that’ll be all.
About changing menu colors currently we don’t have option to change those but you can change the background color from theme option->skin settings. And you’ve to do some custom css to achieve the color you want.
Hope this will help you, if not feel free to let us know.