It is extremely difficult if not impossible to say exactly what colour any barrels should be as tastes and perceived 'correctness' have undoubtedly changed over the last 150 years. However it is reasonable to assume that it wasn't 'black and white', it wasn't called 'browning' by accident.
My preference is for a brown the colour of slightly grey milk chocolate. I use traditional solutions of my own construction and, as far as I am aware, traditional methods of (very) slow rust browning and this is the colour I land up with.
I don't use logwood as my experiments haven't shown any justification for its use but maybe I just don't have the knack.
I do clean up with dilute sulphuric acid to enhance the contrast but leave it that.
I seal with good old gun oil after a long soak in warm, dilute sodium hydroxide solution to neutralise all the acids.
