Summary

This thing consists of small changes to http://www.thingiverse.com/thing:49733:

1. allow 2 mm thickness, so it does not break as fast (plastic is not gold)
2. allow dual extrusion, so every other link can be another color

Dual printing is tricky, a good slicer is required. I succeeded with ReplicatorG. Write a message with your setup if you succeed!