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

对于Swift 4.0, X-code 9.1版本或iOS 11，您可以使用以下语法来拥有不同的占位符颜色

textField.attributedPlaceholder = NSAttributedString(string: "Placeholder Text", attributes: [NSAttributedStringKey.foregroundColor : UIColor.white])

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
    }
}

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

这里我正在写UITextField的所有UIDesignable。在这段代码的帮助下，你可以直接从storyboard中的UI文件Inspector中访问它

@IBDesignable
class CustomTextField: UITextField {

@IBInspectable var leftImage: UIImage? {
    didSet {
        updateView()
    }
}

@IBInspectable var leftPadding: CGFloat = 0 {
    didSet {
        updateView()
    }
}

@IBInspectable var rightImage: UIImage? {
    didSet {
        updateView()
    }
}

@IBInspectable var rightPadding: CGFloat = 0 {
    didSet {
        updateView()
    }
}

private var _isRightViewVisible: Bool = true
var isRightViewVisible: Bool {
    get {
        return _isRightViewVisible
    }
    set {
        _isRightViewVisible = newValue
        updateView()
    }
}

func updateView() {
    setLeftImage()
    setRightImage()

    // Placeholder text color
    attributedPlaceholder = NSAttributedString(string: placeholder != nil ?  placeholder! : "", attributes:[NSAttributedString.Key.foregroundColor: tintColor])
}

func setLeftImage() {
    leftViewMode = UITextField.ViewMode.always
    var view: UIView

    if let image = leftImage {
        let imageView = UIImageView(frame: CGRect(x: leftPadding, y: 0, width: 20, height: 20))
        imageView.image = image
        // Note: In order for your image to use the tint color, you have to select the image in the Assets.xcassets and change the "Render As" property to "Template Image".
        imageView.tintColor = tintColor

        var width = imageView.frame.width + leftPadding

        if borderStyle == UITextField.BorderStyle.none || borderStyle == UITextField.BorderStyle.line {
            width += 5
        }

        view = UIView(frame: CGRect(x: 0, y: 0, width: width, height: 20))
        view.addSubview(imageView)
    } else {
        view = UIView(frame: CGRect(x: 0, y: 0, width: leftPadding, height: 20))
    }

    leftView = view
}

func setRightImage() {
    rightViewMode = UITextField.ViewMode.always

    var view: UIView

    if let image = rightImage, isRightViewVisible {
        let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 20, height: 20))
        imageView.image = image
        // Note: In order for your image to use the tint color, you have to select the image in the Assets.xcassets and change the "Render As" property to "Template Image".
        imageView.tintColor = tintColor

        var width = imageView.frame.width + rightPadding

        if borderStyle == UITextField.BorderStyle.none || borderStyle == UITextField.BorderStyle.line {
            width += 5
        }

        view = UIView(frame: CGRect(x: 0, y: 0, width: width, height: 20))
        view.addSubview(imageView)

    } else {
        view = UIView(frame: CGRect(x: 0, y: 0, width: rightPadding, height: 20))
    }

    rightView = view
}


@IBInspectable public var borderColor: UIColor = UIColor.clear {
    didSet {
        layer.borderColor = borderColor.cgColor
    }
}

@IBInspectable public var borderWidth: CGFloat = 0 {
    didSet {
        layer.borderWidth = borderWidth
    }
}

@IBInspectable public var cornerRadius: CGFloat = 0 {
    didSet {
        layer.cornerRadius = cornerRadius
    }
}
@IBInspectable public var bottomBorder: CGFloat = 0 {
    didSet {
       borderStyle = .none
        layer.backgroundColor = UIColor.white.cgColor

        layer.masksToBounds = false
     //   layer.shadowColor = UIColor.gray.cgColor
        layer.shadowOffset = CGSize(width: 0.0, height: 1.0)
        layer.shadowOpacity = 1.0
        layer.shadowRadius = 0.0
    }
}
@IBInspectable public var bottomBorderColor : UIColor = UIColor.clear {
    didSet {

        layer.shadowColor = bottomBorderColor.cgColor
        layer.shadowOffset = CGSize(width: 0.0, height: 1.0)
        layer.shadowOpacity = 1.0
        layer.shadowRadius = 0.0
    }
}
/// Sets the placeholder color
@IBInspectable var placeHolderColor: UIColor? {
    get {
        return self.placeHolderColor
    }
    set {
        self.attributedPlaceholder = NSAttributedString(string:self.placeholder != nil ? self.placeholder! : "", attributes:[NSAttributedString.Key.foregroundColor: newValue!])
    }
}

}

在Swift中这样使用，

 let placeHolderText = textField.placeholder ?? ""
 let str = NSAttributedString(string:placeHolderText!, attributes: [NSAttributedString.Key.foregroundColor :UIColor.lightGray])
 textField.attributedPlaceholder = str

在Objective C中

NSString *placeHolder = [textField.placeholder length]>0 ? textField.placeholder: @"";
NSAttributedString *str = [[NSAttributedString alloc] initWithString:placeHolder attributes:@{ NSForegroundColorAttributeName : [UIColor lightGrayColor] }];
textField.attributedPlaceholder = str;