...Batman is supposed to be wearing black, while Alfred is wearing- what?
There is an inconsistency underneath all of this, certainly, but I don't find that problematic. Batman used to wear black and grey, now sometimes wears blue. If I had to impose a logical sequence on the matter, then I would submit that the "new look" costume of 1964 onwards introduced the yellow oval and made blue mean blue.
No...the earlier Batman artists had issues with black, and so used blue. Its apparent that from about his second year onward, artists started considering him blue and gray. He was very much intended to be wearing blue in the 70's, and long before that as well.