I'm no scientist but I would think a clay chip that is made up of any color would have the same, as you call melting temperature. After all the entire chip is mostly made up of clay including the inserts, the color is just added additive to the clay. Clay is a porous material that would take on any additive to distinguish colors of a chip, mold or inserts. And in my example, the insert is dark gray.
I also just looked at my notched Atlantis 5000 chip, and it to has the inserts going a lot more than a micron or 0.000039 inch