This is a neat idea -- using a temperature range for extrusion that can cross the color-changing range to allow multicolor 3D printing. This same basic idea --

This is a neat idea -- using a temperature range for extrusion that can cross the color-changing range to allow multicolor 3D printing. This same basic idea -- filament properties that change dramatically across the relatively small extrusion temperature range -- has been explored recently with foaming agents. The first I ran across was lightweight PLA, where by controlling temperature the amount of foaming is adjusted for about a 2x variation in density. Beyond that, I know that lightweight ASA is out there. Probably the most interesting use of foaming agents I've seen is with TPU, though, where the variation in density is less important than the variation in durometer, again over a pretty wide range.