A rainbow, either or not between clouds appears in some degrees, most notably the Ark Mariner, where the colours are part of the regalia.
Together with the rainbow there can be the Laws of Moses. In the symbolism of Noah, also outside Freemasonry, there is often a combination of a rainbow and an ark. There the rainbow represents the covenant between Noah and God.
Also see dove, olive branch and Ten Commandments.
When in combination with a pot of gold, it is an emblem of the Rainbow Girls, an aligned organisation for girls.
Here we also have a rainbow on a third degree Adoption tracing board. Several of the images are also displayed on the tracing board of the second degree, but the rainbow appear for the first time.
Also see ark, Tower of Babel, Bathing, Calf Offer and Jacob’s Offer.
A rainbow can also be found on the tracing board of the degree of “Knight of the Arch of Seven Colours” (41th degree) of (one of the variations of) Memphis Misraim.
Top: taken from Dabrowski p. 178 “Masonic Symbols”
Middle: Rainbow Girls jewel
Bottom: unnamed and undated manuscript, digitally available on the website of the Bibliotheque Nationale de France (FM4 (1323))