You can't just turn your forumname a certain colour, quite unfourtantly :c.
Those members with coloured usernames are either administrators, moderators, mods-in-training, or member of the seasons. FeralHeart uses a colour-code to sort of 'tell people apart'.
This is the colour code xDD.
Red- Administrator
Blue- Mod In Traning/Moderator/GlobalModerator
Green- Member Of the Season
Yellow/Gold- Members
And for the little symbol codes, do you mean stuff like-
[color=cyan>] [/color>] ? (Without the '>'s)
To get those to work, just type whatever you want to in between [color=cyan>] [/color>]