From the The Morning Chronicle London, September 23, 1805 :
I confess I don't know what a "white fast" or "black fast" are. I've seen some refer to Yom Kippur as a "white fast" because Jews wear white on that day, with Tisha B'Av being a "black fast," but that clearly isn't the meaning here. I cannot figure out what they are talking about, especially saying that the "White Fast" lasts a week and the "Black Fast" several days.
The Aberdeen Journal and General Advertiser for the North of Scotland had essentially the same article two weeks later, replacing "Yesterday" with "Saturday last."
20 years later the London Morning Post of September 17, 1825 had a much better description of the Jewish holidays of the month of Tishrei, showing that not much has changed in the last 196 years.