Maintaining transparent title box in mobile view

Hi, In desktop view, there is a semi-transparent box around the title, for instance in the top slider at http://theholyfish.com/ . Another style is like under the 'photo essays' portfolio on the home page, where the whole image is covered on mouse-over. How can I make either of these styles appear on mobile and tablet view? If you look at the 'photo essays' section on a mobile, some of the first article's title becomes obscured by the bright patch in the featured image. I'm thinking that one way to avoid this would be to have the semi-transparent box appear around the title here. Thanks, Mat.