How to make an object/prefab choose between multiple given positions to spawn into?

I have an object/prefab (redcube) and I want to spawn another bluecube next to the red cube, so that only one of it’s sides touches the other’s. The cube has 6 sides, so I can create 6 Vector3 positions for the bluecube to spawn into. How can I make the bluecube randomly choose one of those 6 positions to spawn into?

i guess this here would be the easiest solution:

private readonly Vector3[] directions =
    {
        Vector3.forward,
        Vector3.back,
        Vector3.up,
        Vector3.down,
        Vector3.right,
        Vector3.left
    };

    private Vector3 getRandomDirection()
    {
        return directions[UnityEngine.Random.Range(0, directions.Length)];
    }

let me know if something is missing/unclear.

Note that this assumes that your cubes are aligned with the world coordinates since you did not specify this any further.