How to store enum values in a NSMutableArray

Wrap the enum value in an NSNumber before putting it in the array:

NSNumber *greenColor = [NSNumber numberWithInt:green];
NSNumber *redColor = [NSNumber numberWithInt:red];
NSNumber *blueColor = [NSNumber numberWithInt:blue];
NSMutableArray *list = [[NSMutableArray alloc] initWithObjects:
                             greenColor,
                             blueColor,
                             redColor,
                             nil];

And retrieve it like this:

MyColors theGreenColor = [[list objectAtIndex:0] intValue];