I play at Poker Stars only and also use the colour codes.
There are 8 colours.
You can use them as you please.
My current system is as follows
Green- tight aggressive
Light blue-loose passive
Dark blue- loose aggressive
Purple-likes to bully do not try to limp
Pink-calling station do not try to bluff
Orange- Steals blinds
Mustard- Rude and obnoxious mute chat
Right now I only play at the 1c/2c NL cash tables and have rarely come across a player that I have tagged with a colour.
I do not tag players in freerolls
because it rarely represents the way they will play if they have actual cash in the game. I also play a lot differently in freerolls so hopefully the ones I play with that make notes have freeroll notes on me which are totally irrelevant.