Starting with the JDK 9 release, a Stage on Mac and Linux platforms will be initially filled using the Fill property of the Scene if its Fill is a Color. An average color, computed within the stops range, will be used if the Fill is a LinearGradient or RadialGradient.
Previously, it was initially filled with WHITE, irrespective of the Fill in the Scene. This change in behavior will reduce the flashing that can be seen with a dark Scene background, but applications should be aware of this change in behavior so they can set an appropriate Fill color for their Scene.