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.

Changes

• Removed the gap (0.2mm) - Better first layer, no longer possible normal colour change
• Separated the numbers from the flaps as new objects - Possibility to add different colours to objects on Multi-Material mode.

Credits

Split-flap counter - Fully printable by Thomas H.