Telerik RadTreeView supports right-click menus for each TreeNode (Context Menus). You can define any number of context menus, assign them a name, and then associate any TreeNode with a context menu using the ContextMenuName property.
You can edit the appearance of the context-menu items by editing the TreeContextItem and TreeContextItemOver Css classes defined in the Styles.css file of the skin. For more details, please check the following articles:
Using Css Classes