It sounds weird, but yes it is possible now. A UK based company, called The Unseen has recently unveiled its new dye, named Fire. Interestingly, the dye allows hair to change between two colors, basically depending on the type of dye used.
Real Science Behind It
The dye stems are created from the process of thermoregulation in the human skin. Due to changes in the environment (the temperature drops or rise), he carbon-based molecules undergo a reversible chemical reaction (which occur in response to certain stimuli).
Due to the difference between the stability of carbon bonds, the reaction produces different absorption of light, finally, creating a different color.
According to the WIRED, Scientist and occultist, Lauren Bowker said: “Because of how we’ve formulated the dye, we’re confident there will be no damage to the scalp, and no significant effect on the hair fibers themselves (no more than typical semi-permanent dyes that is.”
Colors include black to white, blue to white, black (cold) to red (hot) and black to yellow. The temperature required to change color depends upon the type of dye. For example, the blue to white dye will activate at 15°C (59°F) and the red to black dye activates at 31°C (88°F).