I believe that *Pad¹ does what you describe. In multi-user mode, it has an option to show each contributor's writing in a separate color. (I'm not sure if one c

I believe that *Pad¹ does what you describe. In multi-user mode, it has an option to show each contributor's writing in a separate color. (I'm not sure if one can pick the color, though.) ¹ eg https://cryptpad.piratenpartei.de/pad/ https://cryptpad.piratenpartei.de/pad/