Swift 3(可能是2)，你可以覆盖didSet占位符在UITextField子类上应用属性，这样:

override var placeholder: String? {

    didSet {
        guard let tmpText = placeholder else {
            self.attributedPlaceholder = NSAttributedString(string: "")
            return
        }

        let textRange = NSMakeRange(0, tmpText.characters.count)
        let attributedText = NSMutableAttributedString(string: tmpText)
        attributedText.addAttribute(NSForegroundColorAttributeName , value:UIColor(white:147.0/255.0, alpha:1.0), range: textRange)

        self.attributedPlaceholder = attributedText
    }
}

在Swift 3.0中，使用

let color = UIColor.lightText
textField.attributedPlaceholder = NSAttributedString(string: textField.placeholder, attributes: [NSForegroundColorAttributeName : color])

在Siwft 5.0 +使用

let color = UIColor.lightText
let placeholder = textField.placeholder ?? "" //There should be a placeholder set in storyboard or elsewhere string or pass empty
textField.attributedPlaceholder = NSAttributedString(string: placeholder, attributes: [NSAttributedString.Key.foregroundColor : color])

只要把下面的代码写进Appdelegate的didFinishLaunchingWithOptions方法，如果你想在Swift 4.2编写的整个应用程序中进行更改，使用这个方法

UILabel.appearance(whenContainedInInstancesOf: [UITextField.self]).textColor = UIColor.white

yourTextfield.attributedPlaceholder = NSAttributedString(string: "your placeholder text",attributes: [NSForegroundColorAttributeName: UIColor.white])

为迅速

func setPlaceholderColor(textField: UITextField, placeholderText: String) {
    textField.attributedPlaceholder = NSAttributedString(string: placeholderText, attributes: [NSForegroundColorAttributeName: UIColor.pelorBlack])
}

你可以用这个;

self.setPlaceholderColor(textField: self.emailTextField, placeholderText: "E-Mail/Username")

Swift 4:

txtControl.attributedPlaceholder = NSAttributedString(string: "Placeholder String...",attributes: [NSAttributedStringKey.foregroundColor: UIColor.gray])

objective - c:

UIColor *color = [UIColor grayColor];
txtControl.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"Placeholder String..." attributes:@{NSForegroundColorAttributeName: color}];