SL does not have a place where you can choose to change your chat and such to different colors. SL uses "color codes" to use colors. There are many colors in SL. To use a color, you must put ` then a number, letter, or symbol. Example:
If you wanted to say "Hey" in red color, you would type in`4Hey
The `4 being the code for red. You can try out different letters, numbers, and symbols to figure out other colors.
Note: Colors cannot be used in naming a weapon, naming an armor, or in a clan name.