I have the Twenty Twelve theme. On the thumbnail images, i have the Title Attribute filled in but I don't like the color theme i.e. yellow background. There's a place I can enter the Image CSS Class in the Image Details Advanced Option right underneath the Title Attribute, but I'm new to this and have no idea what to put there to change the background color.
All I want to do is change the text to white and the background to black. Please help!
You can hover over the first book on this page to see what I mean: http://foodforbeauty.net/recommended/books/