If you meant the second material slot, that is for the chunks themselves yes at depth 1. Always apply that to get a material on the destroyed chunks. That’s the not the issue though.
Here’s a screenshot:
As you can see certain areas of the chunks are uncolored, because the texture map for the object looks like this:
So the material does not contain a fully covered texture image. This is done to prevent visible seams where the UVs are cut, which is what happens if you apply a material with a uniform texture image.
So what I need is to disguise this. It doesn’t need to be perfect as the color variations will not be noticeable to the player. Now ideally I’d just make a full background and add it as a background layer by using photoshop. That way the UV seams would be eliminated and I would also not have these uncolored sections on the chunk edges. I do not have photoshop though so I need an alternate method.
My idea was just adding another texture image and putting the original on top of it, having the blend decided by the gray color (I can make it black or white or any color really), so that the background texture image is used in the gray areas, whereas the original texture image is used for the parts that are not gray, ie the texture map specific to the object.