Purple direction arrow trial.
In the early years of development of the magnetic phonecard product, Telecom tried a few different colours for the direction arrow, and finally settled on the green arrow used on the test cards. Toppan printing used a special ink called “CC” ink, patented by them. CC ink when scanned appears purple.
The card illustrated here appears fully green normally, like the green on the left, but as you can see here, appears purple upon scanning. This is a demo card supplied by Toppan to Telecom Australia around 1992, when Telecom was moving printing to Australia.