Following are the tags you can include within your message:
"[B]", "[/B]", "[U]","[/U]","[I]","[/I]","[color:red]","[/color]","[/size]","[size:xx-small]","[color:blue]","[color:cyan]","[color:brown]","[color:yellow]","[color:green]","[color:orange]","[size:small]","[size:x-small]","[size:large]","[size:x-large]","[url]","[\url]"
Each one will be interpreted as follow:
"<b>", "</b>", "<u>","</u>","<i>","</i>","<font color=\"red\">","</font>","</font>","<font size=\"xx-small\">","<font color=\"blue\">","<font color=\"cyan\">","<font color=\"brown\">","<font color=\"yellow\">","<font color=\"green\">","<font color=\"orange\">","<font size=\"small\">","<font size=\"x-small\">","<font size=\"large\">","<font size=\"x-large\">","<a href=...>","</a>"