here's how u do colors
open with [ color= ] (without the spaces)
after the = put the name of the color u want...red, green, blue (there are several shades of blue),etc. you can see the colors that are available if you click on the drop down next to COLOR when you're making a post or replying.
then you close with [ /color ] again, without the spaces
changing the font is the same way, except you're using the word font instead of the word color. for the greek letters, the font name is symbol. for this purpose, our letters are DSQ instead of DST
you add your signature in your user CP under edit profile.