How to do it...

To highlight a material at mouseover, follow these steps:

1. Create a new 3D project.
2. Import the border.png image into your project.
3. Create a 3D Cube in the scene (Create | 3D Object | Cube).
4. In the Project window, create a new Material asset named m_cube. Set its Albedo color to red.
5. Duplicate your material, naming the copy m_cubeHighlighed. Set the Albedo image for this new material to border:

6. In the Hierarchy window, select the Cube GameObject and assign it m_cube Material. To do so, drag the asset file from the Project window onto the GameObject.
7. Create a new C# script class called MouseOverSwap and add an instance object as a component to the cube:

using UnityEngine;

public class MouseOverSwap : MonoBehaviour 
{
  public Material mouseOverMaterial;
  private Material _originalMaterial;
  private...