It’s probably clear by now but the short answer to the OP is that primary rainbows always have red on top and secondary rainbows always have red on the bottom.
The rainbow itself is caused by the reflection of sunlight by raindrops. Because of the spherical shape of the raindrops, the reflected rays are concentrated at a particular angle. The exact value of this angle depends on the index of refraction, which depends, in turn, on the frequency (i.e. color) of the light. The physics governing this process aren’t susceptible to changes because of atmospheric conditions or viewing aspects.
The secondary rainbow (the higher one in a double rainbow) is formed from light that is twice reflected in the raindrop. There are, of course, tertiary and higher rainbows but 1) they are getting pretty dim (not much light is reflected three times or more) and 2) the third and fourth reflections exit out the back of the raindrop, so in order to see them you would have to face the sun. (An ordinary rainbow is only visible when you’re facing away from the sun. The center of the arc is at the antisolar point.)
The area between the primary and secondary bows is known as “Alexander’s Dark Band” (really), named for Alexander of Aphrodisias, an old Greek. It’s dark because that’s where the light that’s being reflected would be if it weren’t reflected.
Inside the primary bow there are sometimes pink and green alternating bands of color, known as supernumerary arcs.
Finally, larger raindrops are better at separating colors and since raindrops tend to get larger as they fall, rainbows tend to be more intense at the bottom (right near the pot o’ gold). Very fine, misting rain tends to create washed out bows. There is even a phenomenon known as a “fog bow”, created by fog droplets, which is almost white.
pluto, who was once enamoured with rainbows.
“Vandelay!! Say Vandelay!!”