Scientists at the Barcelona Institute of Science and Technology (http://bist.eu/) (BIST) have published a new research paper (https://pubs.acs.org/doi/10.1021/acs.nanolett.8b01164), showing a way to 3D print colored objects using SLS printers.
The technology discussed in the paper shows the possibility of mixing polymer powders with commercial inks to enable on-demand 3D color printing using inkjet based methods by introducing nano materials.
Nanoparticles enable on-demand SLS 3D color printing - 3D Printing Industry (https://3dprintingindustry.com/news/nanoparticles-sls-3d-color-printing-137604/)
This appears to be a substantial development in 3d printing technology.