First off I cannot take any credit for this excellent model. It's created by 3DPrinty - please support the original creator by jumping across and liking/downloading their models. Original files and instructions are all there.

https://www.printables.com/@3DPrinty

This puzzle box is one of the nicest looking, challenging, and satisfying puzzles I've seen - I wanted to print quite a few for gifts, but the original print time with my settings was 20 hours as there was at least one colour change per layer, which means no choice but an overnight (unsupervised) print.

I've reduced the print time from 20 hrs to 13 hrs, and the colour changes from 395 to just 123, by splitting up and painting the model internals the same colour as the external surfaces. It's almost impossible to tell from the outside, but for me this makes it possible to print the model throughout the day where it can be checked on periodically. And with ⅓ the colour changes, its 3x as likely to print without error :-)

I also added a test plate to see how the filaments will contrast on the top of the dial.

Before:

After:

Internals change colour on the same layer as externals (including the dials)