Can a gecko change colore

A gecko does not change colour. the physical appereance of any gecko can alter from a really high contrast to low. This is what hobbyist's reffer to as "firing up" or "firing down". Like humans geckos have pigments in their skin. These pigments are able to lighten and darken depending on a few factors:

• A gecko will fire up when exposed to UVB lighting.
• A gecko will fireup when stressed.
• Depending on being diurnal or nocturnal, a gecko will fire up when active.

Gecko species do not change colour but they will fire up or down.

This is why a high red specimen will usually look salmon/pink/white during the "fired down" phase and within minutes, even seconds can turn to an intense red.