Lightbox – change background color, opacity, close icon, etc.

Change background color and opacity around the lightbox:

#cvpboxOverlay {
    background: #000 !important;
    opacity: 0.5 !important;

Change the border of the lightbox:

#cvpboxLoadedContent {
    border: 5px solid #000 !important;

Change the close icon:

#cvpboxClose {
    background: url(URL_OF_YOUR_CLOSE_ICON_HERE) !important;

Lightbox of thumbnail: change styles of the title (the text on top left of lightbox)

#cvpboxTitle {
    font-size: 20px;
    color: #ccc;
    font-family: Arial, serif;