For non Bambu users used the pause feature on the slicer you use to change colors at the following layer heights

Print at 99% infill with a layer height of 0.16mm with a base layer of 0.18mm

Swap Instructions:
Start with Black
At layer #3 (0.82mm) swap to Gray
At layer #6 (1.14mm) swap to Gray
At layer #8 (1.62mm) swap to White for the rest.