方法1：

cell.textFiled.attributedPlaceholder= [[NSAttributedString  alloc]initWithString:@"Placeholder"attributes:@{NSForegroundColorAttributeName:[UIColor whiteColor]}];

方法2：

textField.placeholder=@"placeholder";

[textField  setValue:[UIColor  redColor]forKeyPath:@"_placeholderLabel.textColor"];

[textField  setValue:[UIFont  boldSystemFontOfSize:16]forKeyPath:@"_placeholderLabel.font"];