Q. Is there a minimum shiur of rainbow that has to be seen in order to make the beracha… (in regards) to the number of colors?
A. Ya'aros D'vash (drush 14) quoting the Zohar explains that there are two kinds of rainbows to be observed. One is the result of the natural phenomena of the refraction of light; the other is an uncommon one that reminds us of the covenant that Hashem made with His creation after the Mabul. S'forim debate the meaning of the Ya'aros Dvash, some assert that the difference rest in the number of colors present or the reversal of the order of them.
However, we customarily do recite a brocho for the common rainbow we see after the rain. The Zohar (Pinchas p. 230) does mention three basic colors and explains their symbolism. Rabenu Bachya (p. Noach) presents a similar idea of three basic colors, which seem to be the three primary colors, red, green (or yellow) and blue (see also explanation in Mitzion Orah p. 69).
Horav Shlomo Miller's Shlit"a opinion is similar to the prior question. If most people would recognize the phenomenon as a rainbow, a brocho can be recited.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit"a
Important Numbers
