Defining a number of gameobjects from another gameobject

I have three cubes: cube1, cube2, cube3. I also have a sphere which controls those cubes. On the sphere there's a script where the three cubes are defined as public gameobjects. I dragged and dropped my cubes into the slots in the inspector. Now what I need to do is for example change the color of those 3 cubes through my sphere controller script. How should I do that? I can use Array, but in this case I would have to tag my cubes, then use GameObject.FindWithTag... And I don't want to do that. Is there a way to define those 3 cubes by just having one variable for all of them?