Hi, flashyn.
There isn’t any theme option to turn off the lightbox site-wide.
If you look in the ‘assets/js/onLoad.js‘ file, at line 116 or thereabouts you will see the following chunk of code:
// generic all links to images selector
$("a[href$='.jpg'],a[href$='.jpeg'],a[href$='.png'],a[href$='.gif'],a[href$='.tif'],a[href$='.tiff'],a[href$='.bmp']").colorbox({
maxWidth: '90%', maxHeight: '90%',
opacity: cb_opacity,
close: cb_close,
next: cb_next,
previous: cb_prev
})
That’s the code that is adding the popup lightbox feature to all image links. If you remove or comment out this code then image links will not be modified by this code.
Always keep in mind that if you modify the core theme files then when you need to update the theme your modified files may be overwritten and your modifications lost. Tweaks to CSS can be added to your Custom CSS box in Theme Options. If you feel that you need to modify CSS files consider using a custom stylesheet, if you feel that you need to modify PHP files consider creating a child theme, otherwise updating the theme may become difficult for you.