When working on no signal, I noticed that some of my fuse boxes were setting the colors of other fuse boxes on accident because they were duplicated from existing fuse boxes.
This was a problem, because the fuse box prefab
                    had some exported NodePaths that were
                    meant to only be used internally, but they were
                    exported so that the field could be set differently
                    based on what kind of fuse box it was (some fuse
                    boxes only need one NodePath while
                    others may need three).
Since some of the fuse boxes were duplicated, the
                    values of the exported NodePaths were
                    copied in the duplicate instead of using the default
                    value from the prefab. This was fixed by having the
                    fuse box find the NodePaths itself by
                    looking for a special path internally. In the
                    future, I should remember to only export fields I
                    want the user to configure when it is instantiated
                    instead of also including fields that I want to use
                    internally.