What Color Is Biblical Blue?

Moshe Abrams writes:

The biblical word t’khelet appears numerous times in the Torah and Talmud. However, it isn’t easy to translate. It denotes a color that the Talmud compares in various places to the color of the sea, the sky, grass, and trees, but never explicitly defines. Could you help elucidate the matter?

A lot has been written on the subject of t’khelet (pronounced t’KHEY-let), much of it summarized in an excellent article by a young rabbinical scholar, Efraim Vaynman, that Mr. Abrams has sent me with his query. For the most part it has to do, like the query itself, with t’khelet’s color, knowledge of which was lost to Jewish tradition after the talmudic period. Vaynman thinks this was violet or purplish-blue and I think he is right.