To change colour name go to single player profile selector in WC3 and create new profile with generated colour code.
Here is how to create colour code:
|c00 - you start with this text, it is telling game that text will be in colour.
Now you need hex code of colour you want, you can use http://www.free-webmaster-tools.com/colorpicker.htm to get colour codes.
Hex colour codes are in for of #00FF00 (this is code for lime colour). You only need code without #.
So only 00FF00
00FF00 - represents colour of text.
And at end your name. Because of character limitation you can only use 5 characters.
Final code will look like this:
Now this paste in profile creator in WC3
For network play is same. In player name paste the code.
NOTE: In network play you will not see your name in colour but other players will