inspired by http://whatcolourisit.scn9a.org

nsdate+color.swift

extension NSDate {
    var color: UIColor {
        let components = NSCalendar.currentCalendar().components(.CalendarUnitHour | .CalendarUnitMinute | .CalendarUnitSecond, fromDate: self)
        let rgb = [components.hour, components.minute, components.second].map {
            CGFloat(strtoul(String($0, radix: 10), nil, 16)) / 255
        }

        return UIColor(red: rgb[0], green: rgb[1], blue: rgb[2], alpha: 1)
    }
}