Here's a similar thing that worked for my project.
HTML
//I "display:none" the images gallery to hide them...
//...then when I click on this JPG image the group of images (above) appear in a colorbox
Here's the JQUERY
$(document).ready(function(){
//when i "click" on the image with a class of "circle1" it opens the "example1" group
$('.circle1').click(function() {
$("a[rel='example1']").colorbox({open:true});
});
});