修改字符串指定范围的颜色

    UILabel *textLab = [[UILabel alloc] initWithFrame:CGRectMake(spaceW, totalPriceLab.height+totalPriceLab.y, payView.width-2*spaceW, 30*KSCALE_HEIGHT)];
    NSString *timeStr = @"30分钟";
    NSString *textStr = [NSString stringWithFormat:@"下单后，请在%@内完成付款",timeStr];
    NSMutableAttributedString *attrDescribeStr1 = [[NSMutableAttributedString alloc] initWithString:textStr];
    [attrDescribeStr1 addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:[textStr rangeOfString:timeStr]];
    textLab.attributedText = attrDescribeStr1;
    [payView addSubview:textLab];