I have gathered many photos from about the last six months of FDM printing. Just for seeing what can be done with one, two and three filament colors. The Geeetech A20M and A20T are single nozzle so colors can be mixed to produce colors other than what are on the feed spools. The present limit in the machine firmware (Marlin) is six (6) colors.  Using a piece of special software called ColorMixer from Geeetech, the prime colors can be mixed and blended layer by layer. You will see here, many creative options.