A Colorbox jQuery Plugin developer designs and maintains the Colorbox jQuery Plugin, a lightweight customizable lightbox plugin for jQuery. This involves writing, testing, and debugging code in the jQuery JavaScript library. They also ensure the plugin is responsive, capable of displaying various content types such as photos, group photos, slideshows, AJAX, inline, and iframed content. They work to optimize the plugin for different browsers and devices, and may also handle user feedback and troubleshooting. Additionally, they may create and maintain documentation to assist other developers in understanding and using the plugin effectively.