Formlabs knows a thing or two about 3D printing materials: it employs an in-house team of materials scientists that work on creating reliable materials, for multiple industries, to use with its Form 2 3D printer. In late 2015, Formlabs added its polypropylene-like Durable Resin to its Engineering Materials library, but once it was finally released to the market a few months ago, the color had changed from yellow to frosted clear. Formlabs materials scientist Alex McCarthy recently addressed this color change, and discussed the science behind 3D printing materials and colors, in a Formlabs blog post. Read more at 3DPrint.com: http://3dprint.com/168145/formlabs-resin-colors/