How to write Visual Studio addin for custom text coloring?

I need to write a visual studio 2005+ addin for custom coloring 开发者_如何学运维of some file format (for example, i need to highlight all words "test" in files that has ".test" extension). Is it any good tutorials available? MSDN help is very general and huge :(. Preferable language is C#, but VB or C++ will do too :).

---

This question might help:

Custom syntax highlighting for VS 2008

They talk about building on top of DxCore, which is the base that CodeRush is built on.

---

You will need to write a language service, which is part of VSX (Visual Studio Extensibility)