We are ROC3d tech team (roc3d.com) who engage to research key technics for 3D FDM and ceramic printer. We designed one new cura plugin for mixing 3 color for FDM printer. Based on multi-section different color zone and Repetier firmware M163, M164 command, you can change virtual Extruder T(n) and treat common Gcode files. You should use Repetier firmware which support M163 instead Marlin, and in the configuration change the extruder number as you want , such as 2, 3,4,...16, also need to choose fitable cura plugin for 2 color mixing, 3 color mixing,....16 color mixing.
We put the cura plugin 2mixing color, 3mixing color for your further improvement, and some picture show the mixing color result. Mixing 3 profile.gcode is profile file for cura, and you can load it with cura. Mixer Mixing 2-10.py is with 10 color section example.
For Diamond hotend, there is defect which is not mxing perfect. The diamond hotend need improve but difficult to install mixing shaft.
Welcome for discussing the mixing color problem.
check : http://reprap.org/wiki/Diamond_Hotend http://reprap.me/media/support/Repetier%20Diamond%20Hotend%20Color%20scripts.txt
-ROC3D team in Zhengzhou China, 9th,July,2016