I think it would be a great idea to allow users to set a personal color within their user settings. This would be the same way as setting a role color, but would instead set their color in all dms to whatever they pick. This could also carry over to servers with a serverwide option to either use personal colors or not. This allows small servers that do not have a traditional role hierarchy to let the users set their own color, and for big servers to still keep a color coordinated system. In addition, personal colors in a server that uses them could be overwritten by a role that does not use the default color.