Best way to save and retrieve UIColors to Core Data

I have made Swift 3 version of Oleg's answer with some modifications on the code.

extension UIColor {
    class func color(withData data:Data) -> UIColor {
         return NSKeyedUnarchiver.unarchiveObject(with: data) as! UIColor
    }

    func encode() -> Data {
         return NSKeyedArchiver.archivedData(withRootObject: self)
    }
}

Swift 5 version of Extension

extension UIColor {

     class func color(data:Data) -> UIColor? {
          return try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? UIColor
     }

     func encode() -> Data? {
          return try? NSKeyedArchiver.archivedData(withRootObject: self, requiringSecureCoding: false)
     }
}

Usage

var myColor = UIColor.green
// Encoding the color to data
let myColorData = myColor.encode() // This can be saved into coredata/UserDefaulrs
let newColor = UIColor.color(withData: myColorData) // Converting back to UIColor from Data

You can convert your UIColor to NSData and then store it:

NSData *theData = [NSKeyedArchiver archivedDataWithRootObject:[UIColor blackColor]];

then you can convert it back to your UIColor object:

UIColor *theColor = (UIColor *)[NSKeyedUnarchiver unarchiveObjectWithData:theData];

UPD.:

Answering your question in comments about storing the data, the most simple way is to store it in NSUserDefaults:

NSData *theData = [NSKeyedArchiver archivedDataWithRootObject:[UIColor blackColor]];
[[NSUserDefaults standardUserDefaults] setObject:theData forKey:@"myColor"];

and then retrive it:

NSData *theData = [[NSUserDefaults standardUserDefaults] objectForKey:@"myColor"];
UIColor *theColor = (UIColor *)[NSKeyedUnarchiver unarchiveObjectWithData:theData];