Do you want different colors, fonts etc. for each category sidebox, or a single style for all of them? Now that you have done all the work to make separate sideboxes, the kind of layout you have currently could easily be done with Categories Dressing in the one original sidebox, using non-linked headings.

Anyway, you can style your current sideboxes with
Code:
.performancesidebox  .sideBoxContent, .exteriorsidebox  .sideBoxContent, .audiosidebox  .sideBoxContent
}