When you're typing a message there are tools you can use above the message box to add a little color to your posts:
Highlight the word/phrase that you want to change the color or font size. Then click on the drop-down arrow next to where it says 'Font Colour' and select one from the menu (same thing for font size).
You can also type in your own codes once you get the hang of using the opening and closing tags. Even if it's just a little bit off, the code won't work and that may be why you were having difficulties.
There are also emoticons to use in your posts. Click on any smiley to the left of the message box when you're typing a message. Click on 'view more emoticons' to see a whole page to choose from.
Hope this helps...give it a try. Let me know if you need any help.
"Never Say Never mixes mischief and heartbreak, dancing on the bar and crying in your beer, in perfect proportion."
-Bill Flanagan, CBS Sunday Morning