Ein HaTecheiles is Rav Binyomin Zev Horvitz’s focused treatment of the color of Techeiles. The kuntres deals with a question that became surprisingly central in the modern Techeiles discussion: what color is the Torah’s Techeiles supposed to be?
Rav Horvitz argues that the plain mesorah, the Gemara’s comparison to the sea and sky, the Rishonim, and the discussion of kala ilan all point to Techeiles being blue. He then addresses the alternate claims that Techeiles may have been green, purple, turquoise, black, or some exact shade that we can no longer identify with confidence.
The sefer is especially useful because it does not treat “blue” as a loose assumption. It opens the sources and works through the language carefully, showing why the simple reading remains the strongest one: Techeiles is the blue associated with the sea, the sky, and the classic understanding of kala ilan.
