BorderColor3 determines the color of a
GuiObject|UI element’s rectangular border (also known as the stroke color).
This is separate from the UI element’s
GuiObject/BackgroundColor3. If you set a UI element’s border and background colors to the same color, you will be unable to distinguish the two.
Other properties properties that determine the visual properties of the border include
Note that you will not be able to see an element’s border if its BorderSizePixel property is set to 0.
This code sample causes a parent Frame to loop through all colors of the rainbow using Color3.fromHSV.
This code sample causes the border of a parent GuiObject to highlight when the user hovers their mouse over the element.