Alter ingame text input?

There were a few people in a server who had bold, red 72 font in the chat. The players claimed it was just HTML, but as I tried it accepted it, but it didn't fully go through. As in I did <B>A, and it just showed A, but not it in bold (Im aware i didnt finish it, its so you can better understand).

learn html and you can do it :P nuff said

there was also a way to type green, ur message has to contain $