Chameleon diamonds are diamonds that change color when exposed to heat or UV rays. Upon exposure to heat, notice how the color of this green diamond changes to yellowish orange. The same occurs upon exposure to UV rays & the heat of the sun. This color change is temporary. Once the diamond is taken away from the heat, the color changes back to its original state (green), in the span of a few seconds. You can observe the same color change phenomenon when it is kept in the dark for over 24 hours.