How to reference compound colliders?

Can we just say GetComponent(Collider)? or do we have to iterate all the children? Wondering if the compound colliders are truly treated as one.

You have to use GetComponents and iterate through the array. So-called Compound colliders don’t exist as such in Unity AFAIK, the program treats a gameobject with one collider the same as one with multiple colliders, that is to say, it’s the colliders themselves that count, not how many “siblings” they have on the same gameobject.