More than a tutorial, this is a walk-through the process of coloring a Mandelbulb 3D fractal.
The original work developed can be found here [link]
I hope this is of some use for you.
Note that this tutorial was made with version 1.7.2 of Mandelbulb 3D, which was current last July 2011. Since then, two new major versions have been issued adding, of course, a lot of new functionalities for coloring like 'Reflections' and 'Color Maps'.
Have a fruitful fractal day!