Haven't looked too far into it, but I think you'll need to manually add the colors to your signature, isabeau.
By that I mean, you'll need to add tags to whatever words you want colored.
So, let's say you want to say something like: "I am Isabeau, the Feather Princess!"
To add colors to it, you'll need tags at the start and the end of the sentence above.
So, you'll do it like this: {color=Yellow}I am Isabeau, the Feather Princess!{/color}
Now, as you can see, there's no pretty yellow color to the above, but if you add brackets like these: [ ] in place of these flourish thingees: { }, you should be able to add color correctly.
Thus: I am Isabeau, the Feather Princess!