/nick <nickname> <player>
Nickname:
With /nickname, codes for coloring and styling are entered before text.
Because of this, nicknames may contain multiple colors and styles.
All
Bukkit color codes are supported.
(!) RGB color codes are supported as well, formatted &#<RGB>
(!) RGB differs from /namecolor in that it requres an & in front of the color.
Text styling uses the same codes as /namecolor