Rainbow username?

[Shana]

How do I set the usernames to be rainbow instead of just one colour? Also, if my name is 'Flowsion' how can I add it to have 'NET' on the END with a different colour? At the moment, I have:

<b><span style='color:#FC0082'>NET</span><span style='color:#3399CC'></b></span>

Thanks!