RadComboBox's visual appearance can be customized through the comprehensive Theming mechanism which Telerik provides, both at design-time or run-time. You can use the Visual Style Builder to create the themes, or load a preset Theme from the dropdown at the top of the example window.

This example also shows the DropDownAnimationEnabled, DropDownAnimationEasing and DropDownAnimationFrames properties of RadComboBox which are used to customize the way the dropdown is expanded and collapsed. For each animation you can specify Type and Duration. The Type is chosen from a list of predefined animation effects. The Duration is set in frames.