修改UITextfield的Placeholder字体的颜色

//第一种

UIColor *color = [UIColor whiteColor];

_userName.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"用户名" attributes:@{NSForegroundColorAttributeName: color}];

//第二种

[_userName setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];

参考地址: http://blog.csdn.net/ck89757/article/details/38730961