Since R1 2018 RadControls are supporting mouse effects. Each element that inherits RadItem support these effects. The effects are allowing you to change the border and the fill while the mouse is over the element. The following image is showing the effects:
EnableHighlightProperty: turns this effect on or off.
HighlightColor: Gets or Sets the color of the effect.
EnableBorderHighlight: turns this effect on or off.
BorderHighlightColor: Gets or Sets the color of the effect.
BorderHighlightThickness: Gets or Sets the highlighted border thickness.