import UIKit

extension UIColor {
    func components() -> [CGFloat] {
        var r = CGFloat(0)
        var g = CGFloat(0)
        var b = CGFloat(0)
        var a = CGFloat(0)
        getRed(&r, green: &g, blue: &b, alpha: &a)
        return [r,g,b,a]
    }
    convenience init?(components: [CGFloat]) {
        guard components.count == 4 else {
            return nil
        }
        self.init(red: components[0],
                  green: components[1],
                  blue: components[2],
                  alpha: components[3])
    }
}

let colors: [UIColor] = [.cyan, .magenta, .yellow, .black]
let serialized = colors.map { $0.components() }

UserDefaults.standard.set(serialized, forKey: "SerializedColors")
let restored = UserDefaults.standard.value(forKey: "SerializedColors") as? [[CGFloat]]

for components in restored ?? [] {
    print(UIColor(components: components) ?? "not a color")
}