Distinguish between two colliding objects

I need to distinguish the two objects of a collision. They are instances of the same prefab, so they have the same name, the same scripts components etc. But i need that when they collide the first one moves an x = +1 and the second one moves an x = -1. I wrote this code but it doesn’t seem to affect the behaviour of the two instances:

function OnTriggerStay (col : Collider){

 if ((col.gameObject.tag == "Enemy"){

 col.gameObject.transform.position += Vector3(1,0,0);
 gameObject.transform.position -= Vector3(1,0,0);
    }

}

I need Unity to distinguish the collider object and the collided object and make the two move a bit in opposite directions. Can you help me?

if u use trigger, you can’t get a collision point and normal to get direction, so you need to calc it based on other info, for example - let’s take pivots of objects

  1. transform.position is
  2. col.transform.position is [he]
  3. [he]- is direction from to [he], call it [dir]
  4. [dir].normalized is direction with length = 1, use it for calculations [dirNorm]
  5. move away from [he] transform.position -= [dirNorm] * length;
  6. move [he] away from col.transform.position += [dirNorm] * length;