Just wanted to clear up a few things.
This cookware is called Visions and it was invented Corning inc.
It is not tempered glass! Tempered glass would be a terrible idea. A small scratch could result in a catastrophic failure of the cookware when heated.
Visions is a glass-ceramic. To make it glass is molded to the desired shape and then the glass is heat treated so that it devitrifies (crystalizes). The crystal structure has a very low CTE so that when it is heated or cooled there only very low stresses on the body, well below the stress needed for failure.
My understanding is that the color is primarily due to the crystal structure, this part could be wrong. My info is from what I recall my wife telling me. She is a glass technologist who worked for Corning for 35 years.
Here is the wiki on visions