Create a simple colored square image. From my UI utils repo https://github.com/mikekatz/iOS-UI-Utils

gistfile1.m

+ (UIImage*) imageWithColor:(UIColor*)color size:(CGSize)size
{
    UIGraphicsBeginImageContext(size);
    UIBezierPath* rPath = [UIBezierPath bezierPathWithRect:CGRectMake(0., 0., size.width, size.height)];
    [color setFill];
    [rPath fill];
    UIImage* image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image; 
}