The Prometheus controls seem to be built on top of the MS AJAX Extensions client-side library, so I believe the only way to use them is to have a MS AJAX Enabled web-page (ScriptManager). rad AjaxManager Prometheus is also built on top of UpdatePanels, so I believe you can use it to ajaxify the color picker.
There might be additional information on this topic in the Prometheus FAQ page:
http://www.telerik.com/products/aspnet-prometheus/faq.aspx