you can only do this if you play via plarium.com there is a thread somewhere deep in the forum
but dont forget dont choose a dark colour or your text will be lost in chat :)
ok lets see if i cn try to help,
when you have your browser open and the game is loaded top right of your screen you should see your name with profile pic click on that then select profile this takes you to your main plarium account page, on that click on profile in profile information click on edit next to your nickname put in the bracket [ type in the colour code you want then close brackets] then type in your nickname, and save, on the left you should now see your profile pic with your name preceded by the bracketed colour code, reload the game then go to your palace select profile and next to your name click on the pencil type icon, now if i remember correctly you should see a copy button click on that and it will copy your nickname from your plarium account profile then click on change name then apply and with all your fingers crossed you name should change colour, ps you cant do this in game you have to change name first in plarium account, and only browser players not sure phone players can do this i could be wrong though,