color printing(ink on paper) has been around for centuries, but was a selective process, applying color to discreet areas(initial caps, image insert pages). and it was a costly and time consuming process. true full color printing which was reporoducable at scale was when chromolithography and color separation process was refined. it was the advances of the halftone screening process that really propelled color printing to enter the mainstream.
3d printing is more complex the its flatland brother, since halftone color process might not be a viable solution to rendering color hues(maybe with multiple hotends). 3d printing is also complicated by the fact that your printing substrate is the "ink" you are using. i've been mulling over 3d printing in color, and my opinion is 6-7 colored filaments, not 5. CMYK+white for color spectrum mixing, grey(cause it's cheaper and faster than mixing expensive pigments) to also be used for infill, and a brittle rafting material.