Because I was curious of the performance difference

Averages

| DispatchOnce   | Static  |         |
|:--------------:|:-------:|:-------:|
| 107            |  342    |         |
| 82             |  408    |         |
| 86             |  365    |         |
| 88             |  357    |         |
| 98             |  375    |         |
| 89             |  356    |         |
| 90             |  357    |         |
| 86             |  351    |         |
| 91             |  362    |         | 
| 99             |  364    |         | 
| 91.6           |  363.7  | Average | 

LogOuput

2014-12-13 15:53:36.646 tester[37460:195541] profile: dispatchOnce: 107 ms
2014-12-13 15:53:36.991 tester[37460:195541] profile: static: 342 ms

main.m

//
//  main.m
//  tester
//
//  Created by Daniel on 12/13/14.
//  Copyright (c) 2014 Daniel. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "AppDelegate.h"

@interface NSObject (Log)
- (void)logTimeTakenToRunBlock:(void (^)(void)) block withPrefix:(NSString*) prefixString;
@end

@implementation NSObject (Log)
- (void)logTimeTakenToRunBlock:(void (^)(void))block withPrefix:(NSString *)prefixString {
    double a = CFAbsoluteTimeGetCurrent();
    block();
    double b = CFAbsoluteTimeGetCurrent();
    
    unsigned int m = ((b-a) * 1000.0f); // convert from seconds to milliseconds
    
    NSLog(@"profile: %@: %d ms", prefixString ? prefixString : @"Time taken", m);
}
@end

@interface UIColor (Thing)
+ (UIColor *)dispatchOnceColor;
+ (UIColor *)staticColor;
@end
@implementation UIColor (Thing)
+ (UIColor *)dispatchOnceColor {
    static UIColor *clr = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        clr = [UIColor colorWithRed:150/255.0 green:125/255.0 blue:67/255.0 alpha:1];
    });
    return clr;
}
+ (UIColor *)staticColor {
    return [UIColor colorWithRed:145/255.0 green:100/255.0 blue:200/255.0 alpha:1.0];
}
@end


int main(int argc, char * argv[]) {
    @autoreleasepool {
        NSObject *obj = [NSObject new];
        
        [obj logTimeTakenToRunBlock:^{
            for (NSInteger i = 0; i < 1000000; i++) {
                UIColor *color = [UIColor dispatchOnceColor];
//                NSLog(@"color - %@", color.debugDescription);
            }
        } withPrefix:@"dispatchOnce"];
        
        [obj logTimeTakenToRunBlock:^{
            for (NSInteger i = 0; i < 1000000; i++) {
                UIColor *color = [UIColor staticColor];
//                NSLog(@"color - %@", color.debugDescription);
            }
        } withPrefix:@"static"];
        
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}