A UK firm called The Unseen has revealed hair dye that can change between two colors if the temperature around you alters.

Called Fire, it was unveiled recently to coincide with London Fashion Week. The dyes allow hair to change between different colors temporarily depending on the type of dye used. This includes black (cold) to red (hot), black to white, silver to blue, blue to white, and black to yellow, according to Forbes. The dyes can be removed after a few washes, without any lasting damage.

The interesting invention works using thermochromic ink, a technology used in things like cans to change the color of text according to the temperature. The Unseen, though, has applied the same technology to hair, without damaging a person’s scalp – as traditional thermochromic ink is toxic.

To deal with this, the firm said in a technical document that they replaced the toxic parts with “less toxic ingredients, which has required a significant amount of reformulation and testing.”

The Unseen also has plans to create a permanent dye, not just a temporary one like this. And there’s scope for more subtle changes too, such as changing color when moving from inside to outside a building (blue outdoors and blonde indoors, for example).

A temperature change from a person’s emotions, such as blushing, could apparently even be enough to change the color of the dye, such as from black to red.

The goal of the product is not just to show off a nifty hair dye, but also to encourage young people to get involved in science and technology.