The problem you had blinkinlovely was that you put the commands in the wrong order. If you are using size and color, you have to put the size first, and you then cancel them in the opposite order at the end, like this but with square brackets...
{size=5}{color=Purple}HELLO{/color}{/size}
You'd put color first and then size. It's a pain, but if you get things in the wrong order it never works.
