blueColor

class MyTextFiled: UITextField {

    override func awakeFromNib() {
       super.awakeFromNib()

    // additional code to make UITextField looking according to your needs
    //placeholder   
       self.text = "Placeholder"
       self.textColor = UIColor.lightGrayColor()

    // bottom line instead of border

}
    
@IBDesignable
class CustomTextField: UITextField {
    override func drawRect(rect: CGRect) {
        super.drawRect(rect)
        // do your custom drawing here...
    }
}

override func awakeFromNib() {
    super.awakeFromNib()
    // initialize properties here...
}
    
UITextField.appearance().backgroundColor = UIColor.blueColor()
    
import UIKit

class MyTextField: UITextField {

  override func drawRect(rect: CGRect) {

    let startingPoint   = CGPoint(x: rect.minX, y: rect.maxY)
    let endingPoint     = CGPoint(x: rect.maxX, y: rect.maxY)

    let path = UIBezierPath()

    path.moveToPoint(startingPoint)
    path.addLineToPoint(endingPoint)
    path.lineWidth = 3.0

    tintColor.setStroke()

    path.stroke()
  }
}