And it came to pass, when Joseph was come unto his brethren, that they stript Joseph out of his coat, his coat of many colors that was on him; Genesis 37:23
This translation is based on the Septuagint, Targum Jonathan and Kimchi. People have often wondered why a trifle like this gaudy garment should have provoke the murderous hatred of all the brethren. We now know from the painted Tombs of the Bene Hassein in Egypt that, in the Patriarchal age, Semitic chiefs wore coats of many colors as insignia of rulership.
Joseph had made himself disliked by his brothers for reporting on them; and Jacob, in giving him a coat of many colors, marked him for the chieftanship of the tribes at his father’s death. Add to this the lad’s vanity in telling his dreams, and the rage of the brethren becomes intelligible.
This sign of rulership was still in use in the household of King David, as is seen from Sam. 23:18, though the chronicler must explain these strange fashion in dress. The fact that in the Joseph story no such explanatory gloss is given is proof of the antiquity of the narrative. When it was first written its implications were perfectly intelligible.
(M. G. Kyle). (Hertz, Dr. J.H., The Pentateuch and Haftorahs, 2nd Ed., Soncino Press, London, 1992, pg 142)