I really liked Thomas H. design, and since I have a Multi-Material printer I didn't do the colour changing method, instead I used the Multi-Material painting feature on PrusaSlicer.
That printed nicely, leaving the parts with multiple colours without the usual colour change on the sides.
↳ Colour change feature (Left) vs Multi-Material painting feature (Right)
However, since the model was designed for the colour change method, i.e. having the number appear at a different layer height, that meant that there was a gap when printing the number on the bottom (0.2mm) and that layer wouldn't end up very pretty.
↳ Original model with 0.2mm gap (Left) vs Multi-Material model without gap (Right)
In order to avoid that I remixed the flaps part.
The author remixed this model.