Paste the following code into a .js file and attach using the Resources section in the in5 dialog:
$(function(){
if($.colorbox) {
$('.lightbox').filter(':not([href*=lightbox\\=0])').colorbox({iframe:true, width:"100%", height:"100%"});
$('svg .lightbox').on(clickEv, function(){
$.colorbox({iframe:true, width:"100%", height:"100%", href:$(this).attr('xlink:href')});
return false;
});
$('.thumb').colorbox({maxWidth:"100%", maxHeight:"100%"});
}
});