Inconsistent Accessibility: Parameter type is less accessible than method

Hi, I can't figure out how to fix this error 'Inconsistent Accessibility: Parameter type is less accessible than method'

this is my code

     public class PlayingCard : MonoBehaviour
     {
      private enum Suits {Diamond,Heart, Club, Spade };
      private enum Color {Black, Red};
      private int _value;
      private Suits _suit;
      private Color _color;


 public static PlayingCard AddNewCard(GameObject gameObject,int value, Color color, Suits suit)
 {
     PlayingCard card = gameObject.AddComponent<PlayingCard>();

     card._value = value;
     card._suit = suit;
     card._color = color;

     return card;


 }

}

// whenever i use my enums in the ''constructor'' my function gets underlined in red and I receive this message : Inconsistent Accessibility: Parameter type is less accessible than method.. Any ideas why ?