NSDictionary *attrDict = @{NSForegroundColorAttributeName : [UIColor redColor]};
NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:textF.placeholder attributes:attrDict];
[textF setAttributedPlaceholder:attrStr];
http://www.jianshu.com/p/e5c6c9b455dd
iOS 设置UITextField的placeholder属性的颜色
原文：http://www.cnblogs.com/fs-ios/p/5033726.html