I generated a 4 color STL of Demon Slayer Giyu with the amazing HueForge program. I used blue colors but you can use any color combination you want but it is recommend to go from dark colors to light colors. if you interested in how I made this file you should check out HueForge its very affordable and only takes some messing around to get used to the program and make amazing looking prints.

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

Filaments Used:
PLA PolyLite Black Transmission Distance: 0.3
PLA PolyLite Azure Blue Transmission Distance: 3
PLA PolyLite Aqua Blue Transmission Distance: 2.5
PLA Polylite Cloud White Transmission Distance: 6

Swap Instructions:
Black until layer #5 at 0.48mm
Azure Blue until layer #9 at 0.8mm
Aqua Blue until layer #17 at 1.44mm
Cloud White for the rest.

The slicer software I used was Bambulab and the printer is the Bambu X1 carbon with AMS.

Keep and eye out if your interested in more HueForge models I plan to upload many more.

Thanks