Is there a list of the styles and what they do?

Dear Christina Wellman,

You can edit css in gallery.css file and jquery.fancybox-1.3.4.css file (in folder: your site/modules/mod_sj_gallery_pro/assets/css)

If you want edit the styles of image popup, you could change css in jquery.fancybox-1.3.4.css file,
and change styles of module, you could change css in gallery.css file.

Thanks