Altering color / alpha on a Game Object

I've brought a model in from 3dmax. It comes in as a main object that has a child object that in turn has 8 child objects. The 8 child objects each have their own Mesh Renderer and Shader. Neither of the parent objects have Meshes.

If I want to apply 50% alpha to the entire model do I need to modify the material.color.a for each item separately? Or is there some way to just apply changes to the parent object?

If they all use the same material, then you can change renderer.sharedMaterial on one of them. Otherwise you have to change each one.