ios改變UITextField的placeholder的顏色

_txtF = [[UITextField alloc]initWithFrame:CGRectMake(0, 100, self.view.width, 30)];
_txtF.font = KFONT_14;
NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:@"請輸入內容" attributes:
    @{NSForegroundColorAttributeName:[UIColor redColor],

 NSFontAttributeName:_txtF.font }]; _txtF.attributedPlaceholder = attrString;
[self.view addSubview:_txtF];