The platonic solid with the least number of faces is the Tetrahedron. Here, it is built on a cube scaffold to find the triangle that uses the GreenLines to build it. If you put a vertex on every face and connect them, you get its dual, also a tetrahedron. 

As part of the Platonic Solids series, this model has clearly defined colors outlining the solid itself, scaffolding in black, and its dual in white.