To add RadColorPicker to an existing ASP.NET web application, follow these steps:
Make sure you have installed ASP.NET AJAX. Info can be found at http://ajax.asp.net/docs/InstallingASPNETAJAX.aspx
If your web application is not using ASP.NET AJAX you need to configure it to do so. Detailed instructions can be found at http://ajax.asp.net/docs/ConfiguringASPNETAJAX.aspx (Look for the topic called "Adding ASP.NET AJAX Configuration Elements to an Existing Web Site".)
Add a ScriptManager control to the page (or user control) in which you want to add any Telerik® UI for ASP.NET AJAX.
If your page is a content page you can add the ScriptManager control in your master page. For further details about the ScriptManager control, see http://ajax.asp.net/docs/overview/ScriptManagerOverview.aspx.
Drag and drop RadColorPicker controls to your web page.