While asking questions in the forum is great, there are a number of resources available to help you find answers to these questions. One is NWNWiki which just so happens to have an article on Text Color.
You used the word "tag" in your query above. I hope you are not putting the color string in the object's tag. If you want to color the name, you should probably be using a color string in the object's name.
For myself, I primarily color text that shows up in the chat window. Have not applied this to object names, although I have seen it done.