I think outside the box so black clandy to me would be a reference to a black man who is clandestine I have never heard the term white clandy just something to think about and mainstream leads one to believe one is superior and the other inferior so I try to reframe from using that as well we must make the necessary corrections in order to move the order forward for the betterment of the craft
From what I have heard, it was a PHA guy that coined the term "mainstream". It was discussed by several PHA freemasons on Prince Hall Think Tank facebook page.