Hi. The Baccarat date canes for 1846, 1847 and 1848 usually have the B - examples without are rare. The cane for 1849 is usually on its own, but a few examples with the B exist. There are also a few examples where the 'B' cane is separate from the date, enclosed in a complex cane. I think the colours within the date vary because they pulled quite a few individual number canes, then combined them as and when needed to make the full date/signature cane. As for why they did not ensure they were all the same colour...who knows!
Alan