Guess I should have uploaded a picture of the main issue. The problem wasn't that the meshes were darker without materials. So since that wasn't the issue I've cleared up my question a bit.

So the coat was one big mesh, I separated it at the top of where it discolored now. It wasn't discolored prior to the separation, the coat looked fine all the way down. It happened after I had mirrored one side of the bottom and had reattached it to the coat again. The texture is fine, it just has a blue hue to it. And I don't know how how to fix it, even with the materials removed, it still has that blue hue to it.
I tried to recalculate outside and inside which had no effect, other than make it look like it should without material. Just like flipping normals did. Any ideas? (Hopefully I explained it good enough)
I found the issue myself yesterday, it's a texture issue. After merging the vertices, the blue area appeared. It's drawing the material from the wrong place in the UV map. How do I go about changing this, in there a way to easily do this, or do I have to move and scale everything by hand?
In the picture, circled in red. It's supposed to be white, but it's blue since it's taking a texture from another part of the UV map, than the rest.