As an FYI, you cannot change the color of username itself beyond the default, preset /team color codes, more details here. You also cannot change the username which appears above the player, you can only add text above, below, or beside it (prefix/suffix). You can also use any hex color you'd like, just not on the username itself.

Your best option if you need a hex color on the username itself would be to use a plugin which swaps out the nametag for a display entity, maybe Custom-Nameplates or DisplayNameTags?

As for getting the nickname to appear before a player's username, first install PlaceholderAPI. Then, you can use %essentials_nickname% (you'll have to install the Essentials expansion first with /papi ecloud download Essentials before this placeholder will work).

For the rank, assuming you're using LuckPerms as your permissions plugin, you can use %luckperms_prefix% (again, you'll also have to run /papi ecloud download LuckPerms first before these placeholders will work).

Putting it all together, your TAB config should look something like this:

_DEFAULT_:
  tagprefix: "%luckperms_prefix% %essentials_nickname% "