Color Changing Hair

There's nothing magic there in the 'color changing' hair.

It's effectively the same effect that we see in most paint stores. In the area where they have their various paint strips, letting you explore the vast rainbow of color options, there is usually a pair of dimmer sliders. One slider controls a fluorescent light, and the other controls a 'natural' light source.

For most colors, the differences in appearance between the two lights is fairly minimal. Most fluorescent lights - particularly older, long tube ballasts - produce a limited spectrum of colors whereas more 'natural' light sources (most incandescent lights and newer, better LED lights) produce a more even spectrum providing each color of light fairly evenly.

Some colors - particularly those in the blue ranges -render very differently in the two different light sources. That's why paint stores provide both light sources, so you can see what the paint will look like in an office with fluorescent lights or outside under the sunlight. For most colors, the difference is minimal, but some show significant differences.

Apparently the dye that this woman has used to color her hair is such a combination of colors.

This video shows a decent comparison of the spectra, but I've struggled to find anything showing a paint under the different qualities of light.