Create a disabled appearance for a button or other SKNode

Button.swift

import Foundation
import SpriteKit

class Button : SKEffectNode
{
    var buttonEnabled: Bool = true {
        didSet {
            if oldValue != buttonEnabled
            {
                updateEnabled()
            }
        }
    }

  private func updateEnabled()
    {
        if buttonEnabled {
            filter = nil
        }
        else
        {
            let desaturateFilter = CIFilter(name: "CIColorControls")!
            desaturateFilter.setValue(0.0, forKey: kCIInputSaturationKey)
            filter = desaturateFilter
        }
    }
}