Changing the material's color in response to mouse events

Another way to indicate a GameObject can be interacted with using the mouse is to just change the Albedo color of the material, rather than swapping to a new material. To illustrate this, we can have one color for mouseover and a second color for a mouse click.

Do the following:

1. Remove the scripted MouseOverSwap from the Cube GameObject.
2. Create a new C# script class called MouseOverDownHighlighter and add an instance object as a component to Cube:

using UnityEngine;

public class MouseOverDownHighlighter : MonoBehaviour {
  public Color mouseOverColor = Color.yellow;
  public Color mouseDownColor = Color.green;

  private Material _originalMaterial;
  private Material _mouseOverMaterial;
  private Material _mouseDownMaterial;
  private MeshRenderer _meshRenderer;

  private bool _mouseOver = false;

  void Awake()
  { 
    _meshRenderer = GetComponent<MeshRenderer>();
    _originalMaterial = _meshRenderer...