How Can we change the theme Color

[KavinduDissanayake]

public class JZWeekViewColors {

class var columnHeaderWeekday: UIColor { return UIColor(hex: 0x757575) }
class var columnHeaderDay: UIColor { return UIColor(hex: 0x757575) }
class var allDayHeader: UIColor { return UIColor(hex: 0x757575) }
class var rowHeaderTime: UIColor { return UIColor(hex: 0x999999) }
class var gridLine: UIColor { return UIColor.clear }

class var today: UIColor { return UIColor(hex: 0x0089FF) }
class var appleCalendarRed: UIColor { return UIColor(hex: 0xFC3D39) }

}

if there any possibility override using an extension or something