http://www.2cto.com/kf/201504/391811.html

NSString *text =@"人生若只如初见";

//判断字符串所在的位置，并不区分大小写

NSRange range = [text rangeOfString:@"若" options:NSCaseInsensitiveSearch];

NSMutableAttributedString *attStr = [[NSMutableAttributedString alloc] initWithString:text];

　　//设置其文字的颜色

[attStr addAttribute:NSForegroundColorAttributeName value:RGBA(0, 161, 176, 1) range:range];

　　//把字符串赋值给label

[self.nameLabel setAttributedText:attStr];