“A prodigy has been born for you. Whoever explains it will restore the child to you.” (Hyginus, Fabulae 136)
When Glaucus, child of Minos and Pasiphae disappeared, Minos made a great search of Crete looking for his son. Finally with not hope remaining he consulted the oracles. The gods responded as above. The “prodigy” was found among Minos’ herds. Wasn’t the first time and won’t be the last; first Zeus as “the white bull, the spotless cloud” (Cox) that sired him on his mother Europa, then the splendid bull of extraordinary beauty the gods sent him, the wooden cow Daedalus designed because of bull and the Minotaur that resulted. ) This prodigy this time was a cow that changes colors; from white, to red to black. The seer Polyidus, son of Coeranus, explained the prodigy by showing that the bullock was like a mulberry tree. For a thorough discussion of what happen next see Lenny Muellner’s paper “Glaucus Redivivus”
No offence to Polyidus, the gathered seers, Apollodorus (Bibliotheca 3.3.1) or Hyginus, but I can think of a better answer.
The bullock in question most resembled a cloud. White with gold tint on a sunny day. Black when heavy with rain. Ruddy when following the setting sun to his western home. Clouds like the Vedic god Indra won.
“Indra shatters Vrtra with his bolt . He cleaves the mountain, making the streams flow or taking the cows, even with the sound of his bolt.. He releases the streams which are like imprisoned cows or which, like lowing cows, flow to the ocean. He won the cows and Soma and made the seven rivers to flow.” AA MacDonell 1
MacDonell’s “many-horned swiftly moving cows” are what Cox calls “golden tinted clouds or herds of Helios”. 2 Helios cows were white with gold horns3 as were Apollo’s. 4 Geryon’s kine grazing in the far west were red.5 Hades’ grazing nearby were black.6 And finally Hera had a cow named Io which changed in color from white to black to violet. 7
So there you go, whether you prefer mundane clouds or the divine kine, both answers are better than Polyidus’.
1 VEDIC MYTHOLOGY BY A. A. MACDONELL. ATMOSPHERIC GODS. 22. INDRA. 59
2 Chapter 38 MYTHOLOGY OF THE ARYAN NATIONS.
3 Apollonius Rhodius Argonautica 4.965
4 Homeric Hymn to Hermes and Philostratus Eder 1.16-31
5 Apollodorus, The Library 2.106-108
6 Apollodorus Bibliotheca 2.125
7 Suida Isis