According to an article in The Business Standard, Bangladesh Bank planned to introduce a new 50-taka note on 15 December 2019. The existing 50- and 10-taka notes (B351 and B349, shown below) are similar in color, leading to confusion in public transactions. The new 50-taka note (B351.5a) is reddish orange to help distinguish between the denominations. The new notes will circulate in parallel with the existing notes.
Courtesy of Mohammad Raihan.