The colour of London Porter

Do you remembering me mentioning about beer styles changing colour? I mentioned that maybe even Porter would have, if the colour hadn't been so strongly associated with it. This passage suggests that I may have been a little hasty in that regard, too.

See what you make of it.

OF THE COLOUR OF LONDON PORTER.
London porter has of late years become of nearly the same colour as Dantzic black beer, which is, perhaps, another improvement of the present day. This alteration in the colour is said to have been adopted merely to humour the public taste. It is very doubtful, however, if the public have been consulted upon the subject, or ever had any voice in the matter. Owing to the causes already mentioned, porter of a brilliant colour, as formerly, is seldom now to be seen ; and the common porter, as generally drunk out of pewter pots, is often so muddy as to be complained of as being unpleasant to the eye. It is just possible, that, to please the public taste as to colour, it may become necessary to make it (the porter) as black as ink ; and this may also be a means of preventing the public from judging whether that which they drink is muddy, or grey, or sometimes even both. This opinion, however, is merely a surmise, which may or may not be the case. It cannot, however, be considered by the public as any very great improvement, inasmuch as it is even now occasionally called, in common parlance, black beer, or black strap."
"A Practical Treatise on Brewing, Based on Chemical and Economical Principles" by William Black 1849, Page 246.

He mentions "porter of a brilliant colour" and porter "as black as ink". It sounds to me as if Porter had become darker in colour. Given the date, I would assume from the use of black malt. The brilliant-coloured Porter he is nostalgic for is presumably from the period 1810-1830. At that time London brewers had grists that were 65% pale malt and 35% brown malt. How dark would such a beer be?

My guess would be that Porter changed colour a couple of times between 1780 and 1840.

1. 1780 - dark brown beer brewed from 100% brown malt
   
2. 1800 - paler brown beer brewed from 65% pale and 35% brown malt
   
3. 1840 - black beer brewed from 85% pale, 12% brown, 3% black malt
   

What do you think?