Fig. 3: Colour mixing (CMYK) with SLS via use of primary coloured coated PA-12 materials.

A Physical mixing of yellow and blue PA-12 materials yielding a green powder composed of unique yellow and blue particles, which when sintered form a structure with a solid green colour. B Graph on CIELAB colour space, showing ≥50 unique colours made through CMYK colour mixing on SLS, with 5 example colours of: Dark Blue, Dark Brown, Violet, Light Green, and Dark Orange. C Example of colour targeting via CMYK colour mixing. Target commercial blue colour (LAB: 48, −3, −42) was achieved through mixtures and surprisingly, only 20% of the blue powder was required to achieve a good match (LAB: 46, −2, −34) to a popular construction toy. We observed a minimal colour difference ∆E (CMC) = 3.5 (0–100 scale with 0 being exact colour match and 100 being complete opposites). D SEM image of cross-section of the print showing successful and uniform sintering of both materials (SEM images were taken in triplicate and in varying magnifications for each sample).