For multi-colour 3D printing, a regular twin extruder 3D printer, one which encompasses a single mount for the dual nozzles, is sufficient. But don’t expect it to be as quickly as an individual extruder 3D printer, looking at the additional excess weight within the print head affects the print speed. https://rafaelrpguh.blogoscience.com/35855985/multicolored-3d-printer-secrets