Murex Used for Indigo

I have read extensively the writings of ancient historians regarding dying with Murex. They describe in fantastic detail the Royal Tyrian Purple that it produced. The fact that it also produced an indigo dye is mentioned virtually nowhere. (An ambiguous and subtle indication of this in Vitruvius is about all you’ll find.) Why is this so?”

R. Tavger explains that in ancient times “purple” referred to all the colors (blues and purples) that come from the snail, and it is only in more modern times when people made a point of differentiating in their speech when talking about the product in general. – Mois Navon