Styling the RadTreeViewItem
The RadTreeViewItem can be styled by creating an appropriate Style and setting it to the Style property of the control or by creating an implicit style.
Targeting the RadTreeViewItem Element
In order to style all RadTreeViewItem elements in a RadTreeView, you should create a style targeting RadTreeViewItem.
Example 1: Creating an implicit style targeting RadTreeViewItem
Figure 1: RadTreeViewItem with Red Foreground in the Fluent theme
You can also use the ItemContainerStyle and ItemContainerStyleSelector properties of the RadTreeView in order to style its items.