This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Tyrian purple on grayscale. 'dibromoindigo the main component of Tyrian purple photographed against gray card and color control patches from my antique color dataguide en Brochis en Brochis original upload log page en Tyrianpurpleongrayscale Brochis bytes no 'dibromoindigo the main component of Tyrian purple photographed