After duplicating a ZenPhoto theme, just with a change of theme directory name and theme name, the Colorbox feature is gone under the new theme. But actually, there is no difference in the theme files, i.e. the coding are the same.
Check the related .php files under the created theme in Option of Colorbox_js plugin
- The specific related theme itself has Colorbox feature and .css, and it is not easy to be aware that there are configuration need to the Colorbox_js plugin. Without check appropriate .php file under each theme, the Colorbox will not properly function.
- There is a standalone Slideshow plugin providing Colorbox feature, however it is not related to this particular theme that has bundled slideshow feature.