Another interesting question is that of Tyrian purple.
Marcus Vitruvius Pollio says the dye was extracted from shellfish in 30 BCE.
Pliny the Elder elaborated on the production of Tyrian purple in his Natural History:
The most favourable season for taking these [shellfish] is after the rising of the Dog-star, or else before spring; for when they have once discharged their waxy secretion, their juices have no consistency: this, however, is a fact unknown in the dyers' workshops, although it is a point of primary importance. After it is taken, the vein [i.e. hypobranchial gland] is extracted, which we have previously spoken of, to which it is requisite to add salt, a sextarius [about 20 fl. oz.] about to every hundred pounds of juice. It is sufficient to leave them to steep for a period of three days, and no more, for the fresher they are, the greater virtue there is in the liquor. It is then set to boil in vessels of tin [or lead], and every hundred amphoræ ought to be boiled down to five hundred pounds of dye, by the application of a moderate heat; for which purpose the vessel is placed at the end of a long funnel, which communicates with the furnace; while thus boiling, the liquor is skimmed from time to time, and with it the flesh, which necessarily adheres to the veins. About the tenth day, generally, the whole contents of the cauldron are in a liquefied state, upon which a fleece, from which the grease has been cleansed, is plunged into it by way of making trial; but until such time as the colour is found to satisfy the wishes of those preparing it, the liquor is still kept on the boil. The tint that inclines to red is looked upon as inferior to that which is of a blackish hue. The wool is left to lie in soak for five hours, and then, after carding it, it is thrown in again, until it has fully imbibed the colour.
Julius Pollux wrote in the 100s CE that the purple dye was first discovered by Heracles, or rather, by his dog, whose mouth was stained purple from chewing on snails along the coast of the Levant.
In Ancient Mesopotamian Materials and Industries: The Archaeological Evidence, it is stated that evidence exists for the extraction of dye from the shellfish H. trunculus and B. brandaris. Both of these shellfish are from the same family, and it is expected the dye from H. trunculus was the most highly prized. The dye from both was probably regarded as "Tyrian purple" in antiquity and probably was often mixed to produce a dark dye similar in color to dark clotted blood. Archeological evidence from Crete suggests that the Minoans may have pioneered the extraction of Imperial purple centuries before the Phoenicians who later mastered the art on an industrial scale.
The production of Tyrian purple came to an abrupt end with the sack of Constantinople in 1204. Economically the market could not sustain the intensive process of extracting the dye from tens of thousands of shellfish. The production continued in Islamic Egypt until the 1300s when it died completely. Instead, vermilion dye (♦♦♦), extracted from the insect Kermes vermilio native to the middle east became the predominant royal dye in the Islamic world and Europe. This continued until the 1700s.
So what about the colors?
H. trunculus produces a deep blue-purple color like this ♦♦♦. This color was rarer and these shellfish reproduce less rapidly.
B. brandaris produces a red-purple color like this ♦♦♦.
When these dyes are mixed, as they likely were in various amounts you get a spectrum of colors like this:
(more expensive) ♦♦♦ ♦♦♦ ♦♦♦ ♦♦♦ (less expensive)