The whole concept of tekhelet fascinates me.  In the third paragraph of the Sh’ma, Jews are commanded to affix a פתיל תכלת, one string of this color “tekhelet” upon their fringes (tzitzit).  Some Jews have revived this tradition in Israel.  Check out this article about how they may actually be right, and the amazing quote:

“Tekhelet is the color of the sky,” Dr. Koren said in his laboratory. “It’s not the color of the sky as we know it; it’s the color of sky at midnight.” He paused and added, “It’s when you are all alone at night that you reach out to God, and that is what tekhelet reminds you of.”

via Israel’s Renewed Interest in a Rediscovered Ancient Color – NYTimes.com.