Re: is there any eatable materials that change color due to temperature change?

There are obviously many foods that change color when cooked. This includes
most meat products, which change from red or purple to gray-brown as the
oxymyoglobin is denatured by heat.

However, it is more likely your question is really, "What foods change
color when warmed in the mouth?".

I don't know of any foods that change color significantly over the range 10
C to 40 C. The most likely candidates would be fats and hydrogels (e.g.,
modified starches or gums with water). When these substances melt, they
change from a white, translucent substance to clear.

If you are trying to make demonstration project, try encapsulating food dye
inside of a fat coating. When the fat melts, the dye would mix with saliva
and make a strong color.

There is a novelty trick of this type available. A special chewing gum that
leaves the mouth black afterwards.