创建一个分类Category： 支持十六进制Hex颜色设置。
新建 -> Objective-c File 选择 Category
只需输入为分类起的名字Hex，会自动生成分类名字的格式 UIColor+Hex

//.h文件
#define RGBA_COLOR(R, G, B, A) [UIColor colorWithRed:((R) / 255.0f) green:((G) / 255.0f) blue:((B) / 255.0f) alpha:A]
#define RGB_COLOR(R, G, B) [UIColor colorWithRed:((R) / 255.0f) green:((G) / 255.0f) blue:((B) / 255.0f) alpha:1.0f]

+ (UIColor *)colorWithHexString:(NSString *)color;
//从十六进制字符串获取颜色，
//color:支持@“#123456”、 @“0X123456”、 @“123456”三种格式
+ (UIColor *)colorWithHexString:(NSString *)color alpha:(CGFloat)alpha;
+ (UIColor *)colorFromHexRGB:(NSString *)inColorString;
+ (UIImage *)imageWithColor:(UIColor *)color ;

//.m 文件  
+ (UIColor *)colorWithHexString:(NSString *)color alpha:(CGFloat)alpha
{
    //删除字符串中的空格
    NSString *cString = [[color stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
    // String should be 6 or 8 characters
    if ([cString length] < 6){
        return [UIColor clearColor];
    }
    // strip 0X if it appears
    //如果是0x开头的，那么截取字符串，字符串从索引为2的位置开始，一直到末尾
    if ([cString hasPrefix:@"0X"]){
        cString = [cString substringFromIndex:2];
    }
    //如果是#开头的，那么截取字符串，字符串从索引为1的位置开始，一直到末尾
    if ([cString hasPrefix:@"#"]){
        cString = [cString substringFromIndex:1];
    }
    if ([cString length] != 6){
        return [UIColor clearColor];
    }
    
    // Separate into r, g, b substrings
    NSRange range;
    range.location = 0;
    range.length = 2;
    //r
    NSString *rString = [cString substringWithRange:range];
    //g
    range.location = 2;
    NSString *gString = [cString substringWithRange:range];
    //b
    range.location = 4;
    NSString *bString = [cString substringWithRange:range];
    
    // Scan values
    unsigned int r, g, b;
    [[NSScanner scannerWithString:rString] scanHexInt:&r];
    [[NSScanner scannerWithString:gString] scanHexInt:&g];
    [[NSScanner scannerWithString:bString] scanHexInt:&b];
    return [UIColor colorWithRed:((float)r / 255.0f) green:((float)g / 255.0f) blue:((float)b / 255.0f) alpha:alpha];
}

//默认alpha值为1
+ (UIColor *)colorWithHexString:(NSString *)color
{
    return [self colorWithHexString:color alpha:1.0f];
}



/*!
 * method 通过16进制计算颜色
 * abstract
 * discussion
 * param 16机制
 * result 颜色对象
 */
+ (UIColor *)colorFromHexRGB:(NSString *)inColorString
{
    UIColor *result = nil;
    unsigned int colorCode = 0;
    unsigned char redByte, greenByte, blueByte;
    
    if (nil != inColorString)
    {
        NSScanner *scanner = [NSScanner scannerWithString:inColorString];
        (void) [scanner scanHexInt:&colorCode]; // ignore error
    }
    redByte = (unsigned char) (colorCode >> 16);
    greenByte = (unsigned char) (colorCode >> 8);
    blueByte = (unsigned char) (colorCode); // masks off high bits
    result = [UIColor
              colorWithRed: (float)redByte / 0xff
              green: (float)greenByte/ 0xff
              blue: (float)blueByte / 0xff
              alpha:1.0];
    return result;
}

//UIColor转换成一张UIImage
+ (UIImage *)imageWithColor:(UIColor *)color {
        CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f); //宽高 1.0只要有值就够了
        UIGraphicsBeginImageContext(rect.size); //在这个范围内开启一段上下文
        CGContextRef context = UIGraphicsGetCurrentContext();

        CGContextSetFillColorWithColor(context, [color CGColor]);//在这段上下文中获取到颜色UIColor
        CGContextFillRect(context, rect);//用这个颜色填充这个上下文

        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();//从这段上下文中获取Image属性,,,结束
        UIGraphicsEndImageContext();

        return image;
}

如何使用：

//直接在其他文件中：
UIColor *myColor = [UIColor  方法名];

各种颜色值参考1
各种颜色值参考2