Input not working outside of unity

I have a simple application with unity that displays a rectangle, and when you press the key “a”, it displays a random color. It works just fine in Unity, but when i build it and run outside of unity, it displays the rectangle but doesn’t do anything when i press “a”. here is my code:

using UnityEngine;
using System.Collections;

public class ColorUI : MonoBehaviour {
	Renderer render;
	void Start () {
		render = GetComponent<Renderer> ();
	}
	void Update () {
		if (Input.GetKeyDown("a")) {
			render.material.color = new Color(Random.value, Random.value, Random.value, 1.0f);
		}
	}
}

You’d have to use Keycode.A

if (Input.GetKeyDown(Keycode.A))