Use this method :
- (NSString *)hexStringForColor:(UIColor *)color {
const CGFloat *components = CGColorGetComponents(color.CGColor);
CGFloat r = components[0];
CGFloat g = components[1];
CGFloat b = components[2];
NSString *hexString=[NSString stringWithFormat:@"%02X%02X%02X", (int)(r * 255), (int)(g * 255), (int)(b * 255)];
return hexString;
}