<p>There is this great hotend called a <a href="http://reprap.org/wiki/Diamond_Hotend#Benefits_of_this_design" rel="noreferrer">diamond hotend</a>, which can be used to print in 3 colors and mix them into hundreds? of colors. This can for example be used with Red, Green and Blue filament to mix a RGB palette. They don't have to be these colors, but I believe RGB would give the maximum range of colors when constrained to 3.</p>

<p>However true RGB in physical printing would use separate colored <a href="https://en.wikipedia.org/wiki/Voxel" rel="noreferrer">voxels</a> to create the appearance of a color, just like monitors display colors. As far as I know only HP Jet Fusion 3D printer uses this process, but it uses a process vastly different from normal diy 3D FDM printers.</p>

<p>CMYK is mixed physically like you would mix watercolors together to make new colors. It is used for printing on paper by <strong>all</strong> laserjet and inkjet printers (and in printing presses).
So that means even the 3 input diamond hotend is actually mixed like CMYK. Repetier firmware v92.9 has this built in with support up to 16 inputs for a nozzle, but Marlin firmware v1.0.x only supports 4 inputs per nozzle at this time.</p>

<p>Using RGB for the 3 inputs of a hotend, means the printing color palette lacks White and also it seems that CMYK would give a bigger range of colors. That brings our tally to 4 inputs. It still needs a white filament to print white, so that means 5 inputs. And while we are at it, probably a 6th input would be useful: like for printing black infill (to save using CMYK to mix into black) or for using transparent filament or elastic filament.</p>

<p>So why isn't there a nozzle with 5-6 inputs already? Could it be done? Are there such hotends already?</p>

<p>P.S These are just theoretical assumptions. I just discovered 3D printing and I am in the planning phase of building my first 3D printer, so I am a total n00b in this. Please correct any assumptions I got wrong.</p>

[{'answer_id': 2908, 'author': 'Carl Witthoft', 'author_id': 2191, 'author_profile': 'https://3dprinting.stackexchange.com/users/2191', 'pm_score': 2, 'selected': False, 'text': '<p>You may be a bit misled here. First of all, you do <strong>not</strong> want "RGB" , as those are additive colors such as used when combining light sources.  You <strong>do</strong> want "RYB" (red-yellow-blue) or the more accurate CMY(plus K just to get a \'truer\' black)  for subtractive colors.</p>\n\n<p>Next, there\'s really no reason to attempt pixel-mixing. What should happen, ideally, is that pigments get fully mixed upon extrusion so that the desired color is actually in place. Pretty much any pixel-based setup will not "blend" into the desired visual perception.  And as you propose, you really need a White and a Black to adjust the saturation (take a look at the Wikipedia pages on Hue and Saturation color maps).<br>\nSo I\'m not convinced that separate extrusion heads will ever get you a decent color continuum.  I don\'t know if anyone has, or is planning, a multi-input, single-output head but I\'d sure like one. </p>\n'}, {'answer_id': 5392, 'author': '3dGenie', 'author_id': 9832, 'author_profile': 'https://3dprinting.stackexchange.com/users/9832', 'pm_score': 2, 'selected': True, 'text': '<p>You can find a full color hot end with CMYK+White if you look here <a href="https://www.reprap.me/diamond-fullcolor-hotend.html" rel="nofollow noreferrer">https://www.reprap.me/diamond-fullcolor-hotend.html</a></p>\n'}, {'answer_id': 5397, 'author': 'Nick Dancer', 'author_id': 9835, 'author_profile': 'https://3dprinting.stackexchange.com/users/9835', 'pm_score': 1, 'selected': False, 'text': '<p>So whilst this is not quite what you were talking about I think this is the closest to the effect you’re looking for that I’ve seen.</p>\n\n<p><a href="https://www.xyzprinting.com/en-US/product/da-vinci-color" rel="nofollow noreferrer">https://www.xyzprinting.com/en-US/product/da-vinci-color</a></p>\n\n<p>This da Vinci printer uses a CMYK inkjet to colour a white filament as its being extruded. This allows for very quick changes in colour as well a nearly infinite combination of colours.</p>\n\n<p>This means it only needs a single extruder and hotend but obviously the hotend needs to be built to allow the injection of pigment from the inkjet.</p>\n'}]
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