set
Returns the border color of this annotation or Color.TRANSPARENT if no color is set. Note that alpha channel is not taken into account as per PDF specifications.
Border color usually redirects to color, unless overridden to have a real backing store (this is the case for WidgetAnnotation).
The annotation will only store the RGB part and discard the alpha channel set here. Annotation opacity is set via the alpha property.
Return
Color of annotations border or Color.TRANSPARENT if no color is set.