I freely admit that this is not a great picture, but rainbows are rare enough here that the kids and I ran outside to see this one, and marveled at it's beauty. Blue mentioned that he had seen a rainbow in Hawaii (thank you, thank you for remembering that - and not the harrowing plane ride there and back).
I like the science of rainbows (and light in general). I like that the rainbow that I see is not the same one that anyone else sees, because it is an optical phenomenon based on the position of the observer (but can be captured by camera). I like that Pink stood on the table outside in her Snow White dress and refused to come in because she was so enthralled.
My two cents worth (probably not even that):
The ROY G BIV thing is bogus. Newton ascribed 7 colors because the number 7 was considered holy in his time. I'm not the only one to say that "Indigo" is not only difficult to see, but doesn't make any sense in terms of the primary and secondary color theory of today. The spectrum is actually continuous, so all colors are there, but if we're going to divide the rainbow into bands, let's be reasonable.
We saw a Supernumerary Rainbow tonight, which is not only rare, but is also impossible to describe with classical geometric optics. The supernumerary rainbow helped demonstrate the wave nature of light - and that's a whole lot more fun than particles alone.
And a little from Wikipedia:
A rainbow does not actually exist at a particular location in the sky. Its apparent position depends on the observer's location and the position of the Sun. All raindrops refract and reflect the sunlight in the same way, but only the light from some raindrops reaches the observer's eye. This light is what constitutes the rainbow for that observer. The position of a rainbow in the sky is always in the opposite direction of the Sun with respect to the observer, and the interior is always slightly brighter than the exterior. The bow is centred on the shadow of the observer's head, or more exactly at the antisolar point (which is below the horizon during the daytime), appearing at an angle of 40–42° to the line between the observer's head and its shadow. As a result, if the Sun is higher than 42°, then the rainbow is below the horizon and usually cannot be seen as there are not usually sufficient raindrops between the horizon (that is: eye height) and the ground, to contribute.