Hoe set background color clear

in my tutorial in storyboard have first view with draw and second view as SKScene for SpriteKit, how set clear color in the scene

in Xcode 10 type GameScene.skn in custom color alpha = 0 but not chage

idem if set in code with type view.backgrondcolor = .clear , it has no effect


how resolve the problem , is possible ????


help

thank