The appearance of the hair’s color depends on primary and secondary color reflection.
The surface texture and the inner structure influence the shine and vibrancy of the hair color.
Light is reflected from the cuticle and from inside the hair. The inside reflection creates color depth.
For hair to have a natural shine, the light needs to be reflected on an even and thus healthy surface where the cuticle lays flat.
Reflected light at back-surface travels inside the hair fiber and reflects the color of hair.
Light can also interfuse the hair, meaning light rays are reflected from inside.
This is known as secondary reflection. If the light rays inside the hair are refracted or diffused by an uneven inner structure, the hair will be less shiny and the color will be less clear.
Light scattering inside the hair, reduces contrast, vividness, depth and transparency.