Image size in Colorbox

Ok I figured it out:

// show ‘large’ image instead of default ‘full’
// in wp-simple-gallery.php file, row 190, $url = wp_get_attachment_url($id); replace with this;
$url_od_large = wp_get_attachment_image_src( $id, ‘large’ );
$url = $url_od_large[0];