Inspired by an answer this question:
However, Rav Yonason Eibshitz in his sefer Yaaros Dvash (chelek 1:drush 12) explains in the name of the Zohar Hakadosh that there are two types of rainbows. There is one which has many stripes of color (the one we see commonly) and then there is the rainbow which is completely blue (techeiles color). He explains that the blue one is the rainbow that is zocher habris because techeiles is from the lashon of kilyon (destruction).
A side note: The Ben Ish Chai parshas Eikev 17 writes that from this drush from Yaaros Dvash it would appear that one should not make a bracha on a colored rainbow since only the blue one is the reminder.
Saying a blessing on a rainbow requires one to see it. What does the blue rainbow refer to physically?