This is an old AGI video department trick for rocket engines, fire, explosions, etc.  `NoDiffuseLighting`, `FaceEmissionColor White`, apply a texture (in this case procedural).  Basically the best artistic control is had by preventing the saturation you mention, and using emission to directly control the output color.  The basic idea is that the object's colors don't react at all to the presence of an external light source, instead it gives off enough of its own "light" to over-expose the center pixels of the polyline (hence white is the innerColor, and the polyline's actual color becomes the "bloom" around the overexposed pixels).  This type of effect can get washed out on light backgrounds, and works best against a [dark background](http://thecoolgadgets.com/wp-content/uploads/2009/07/Jedi-LightSaber-Duo-Pack.jpg).

Is it safe to leave diffuse un-assigned here?  If not I'll add `material.diffuse = vec4(0.0);`