UIColor+Extension

import UIKit

infix operator |: AdditionPrecedence
public extension UIColor {
    
    struct App {
        static let hyperLink = UIColor.colorWithHex(hex: "#FFFFFF")
        static let background = UIColor.white | UIColor.black
    }
    
    static func | (lightMode: UIColor, darkMode: UIColor) -> UIColor {
        guard #available(iOS 13.0, *) else { return lightMode }
        return UIColor { (traitCollection) -> UIColor in
            return traitCollection.userInterfaceStyle == .light ? lightMode : darkMode
        }
    }

    convenience init(r: Int, g: Int, b: Int) {
        assert(r >= 0 && r <= 255, "Invalid red component")
        assert(g >= 0 && g <= 255, "Invalid green component")
        assert(b >= 0 && b <= 255, "Invalid blue component")
        self.init(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: 1.0)
    }
    
    class func colorWithHex(hex: String) -> UIColor {
        
        var colorString: String = hex.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()
        
        // Remove prefix if contain # at 0th position.
        if colorString.hasPrefix("#") { colorString.remove(at: colorString.startIndex) }
        if colorString.count != 6 { return UIColor.gray }
        
        var rgbValue: UInt64 = 0
        Scanner(string: colorString).scanHexInt64(&rgbValue)
        
        return UIColor (
            red: CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(rgbValue & 0x0000FF) / 255.0,
            alpha: CGFloat(1.0)
        )
    }
    
    class var random: UIColor {
        let max = CGFloat(UInt32.max)
        let red = CGFloat(arc4random()) / max
        let green = CGFloat(arc4random()) / max
        let blue = CGFloat(arc4random()) / max
        return UIColor(red: red, green: green, blue: blue, alpha: 1.0)
    }
    
    class func hexValue(color: UIColor) -> String {
        let components = color.cgColor.components
        let r: CGFloat = components?[0] ?? 0.0
        let g: CGFloat = components?[1] ?? 0.0
        let b: CGFloat = components?[2] ?? 0.0
        return String.init(format: "#%02lX%02lX%02lX", lroundf(Float(r * 255)), lroundf(Float(g * 255)), lroundf(Float(b * 255)))
     }
    
    func lighter(by percentage: CGFloat = 30.0) -> UIColor? {
        return self.adjust(by: abs(percentage) )
    }
    
    func darker(by percentage: CGFloat = 30.0) -> UIColor? {
        return self.adjust(by: -1 * abs(percentage) )
    }
    
    private func adjust(by percentage: CGFloat = 30.0) -> UIColor? {
        var red:CGFloat = 0, green:CGFloat = 0, blue:CGFloat = 0, alpha:CGFloat = 0
        if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
            return UIColor(red: min(red + percentage/100, 1.0),
                           green: min(green + percentage/100, 1.0),
                           blue: min(blue + percentage/100, 1.0),
                           alpha: alpha)
        } else {
            return nil
        }
    }
}

Updated code