Im not sure about other slicers, but in Bambu Studio I had to set wall generator to Arcane in order for it to detect the white outline. 

Print at 100% infill with a layer height of 0.08mm with a base layer of 0.16mm

Filaments Used:
PLA+ Sunlu Black 
PLA+ Flashforge Purple 
PLA+ Sunlu Blue 
PLA+ Sunlu White 

Swap Instructions:
Start with Black
At layer #11 (0.96mm) swap to Purple
At layer #15 (1.28mm) swap to Blue
At layer #18 (1.52mm) swap to White for the rest.