How can i make hitboxes?

I cant 100% tell that what iam asking for called hitboxes, but you will undesrtand.
This model just example of what iam asking for. I want to make shooter game and i have some of models that i make in Maya.
I want to make Invulnerable “red part” for different types of weapon, “green part” has most vulnerable points and “yellow parts” just good to shoot.

Hitboxes are just box/other colliders and a bit of scripting. You could make childs of box colliders and have a script for each box collider to how much damage it will recieve