Dynamic colors for Dark and Light modes.

DarkLightModeDynamicColors.swift

// Examples
UIColor.red.tweaked

UIColor.blue.lighter

extension UIColor {
    /// Color gets darker in Light mode and lighter in Dark mode.
    @objc var tweaked: UIColor {
        if #available(iOS 13.0, *) {
            switch UIApplication.userInterfaceStyle {
            case .dark:
                return self.lighter
            case .light:
                return self.darker
            default:
                return self
            }
        }
        return self
    }
}


// Helpers

extension UIApplication {
    static var traitCollection: UITraitCollection? {
        return UIApplication.shared.keyWindow?.traitCollection
    }

    @available(iOS 12.0, *)
    static var userInterfaceStyle: UIUserInterfaceStyle {
        return UIApplication.traitCollection?.userInterfaceStyle ?? .unspecified
    }
}


extension UIColor {
    @objc var lighter: UIColor {
        return self.changedBrightness(by: 1.25)
    }

    @objc var darker: UIColor {
        return self.changedBrightness(by: 0.75)
    }

    func changedBrightness(by amount: CGFloat) -> UIColor {
        var h: CGFloat = 0; var s: CGFloat = 0
        var b: CGFloat = 0; var a: CGFloat = 0

        guard self.getHue(&h, saturation: &s, brightness: &b, alpha: &a) else { return self }

        return UIColor(hue: h, saturation: s, brightness: b * amount, alpha: a)
    }
}