He may have been. However, there is no solid information in that regard, just a series of historical coincidences that make his association with them quite possible.
AnswerThe biblical description of John the Baptist depicts an ascetic who spurned comfort. In this regard, he seems to have been similar to the Essenes. Some scholars believe he may have been a member of the Essene sect.
Essenes
His father was a priest. However, St. John was raised by the Essenes.
Tradition has it that John the Baptist was an orphan and adopted by the Essenes who are Hebrew monks. They wore sackcloth and lived off the land. That is why John the Baptist had such peculiar habits.
When his mother, St. Elisabeth, gave him over to the Essenes to raise him.
AnswerThe Essenes were an ascetic sect that appears to have had a community at Qumran, near the Dead Sea, and produced the documents now known as the Dead Sea Scrolls.There are suggestions that, because of his own acetic life style, John the Baptist may have been an Essene, but there is no real evidence of any link between him and the Essenes.
I believe the colour most closely associated with St John the Baptist is red. Whether or not it was his favourite is the topic of much theological debate and is an issue that still divides the Church.
Essenes
He was raised in the wilderness by the Essenes (his parents gave him over to them to prevent him from being killed by Herod the Great). Then he moved near the Jordan River to baptize people.
They were called the Essenes. They were responsible for the creation of the Dead Sea Scrolls.
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He was raised by the Essenes, after his parents, Sts. Elisabeth & Zechariah took him into the desert, to escape Herod the Great's edict on killing boys 2 years old & under.