How differ in script one of many collider2D components of same type in same gameObject?

For example, I have gameObject with two box collider2D components. I want to change Physics2D Material by script for only specific one of these colliders. But how I can differ these same colliders in script?

If you know beforehand which one you want to change, the easiest would be to add a reference to it in your script:

public Collider2D colliderToCange;

and then change it when you need to.

As an alternative, you can put the two colliders in different child objects.