Is a generic list of UnityEngine.UI.Button possible?

This is the error: The type System.Collections.Generic.List' does not contain a constructor that takes 2’ arguments

public UnityEngine.UI.Button red;
public UnityEngine.UI.Button blue;

public List<UnityEngine.UI.Button> keys;

    void Awake()
    {
       keys = new List<UnityEngine.UI.Button>(red, blue);
    }

    void Start()
{
	for(int teclas = 0; teclas < keys.Count; teclas++)
	{
		Debug.Log("Creating key " + teclas);
	}
}

You’re using the constructor incorrectly… or the overload actually.

 void Awake()
 {
    keys = new List<UnityEngine.UI.Button>(red, blue);
 }

should be and it might look weird to some due to no parenthesis:

 void Awake()
 {
    keys = new List<UnityEngine.UI.Button> { red, blue };
 }

There are other ways of doing this, this is one example