In the chat screen, all 252 of the RGB values have been changed to 251.

Command:

/tellraw @a {"text":"\u00a70■\u00a71■\u00a72■\u00a73■\u00a74■\u00a75■\u00a76■\u00a77■\u00a78■\u00a79■\u00a7a■\u00a7b■\u00a7c■\u00a7d■\u00a7e■\u00a7f■"}