It was an interesting question and hopefully the o/p will do some research of her own. "Things found" are worth a lot more than us coming up with all kinds of supposition. But she did say "rainbow" - the 7 rays of esotericism don't, in their ordering, make up a rainbow but as is the way with the new age the word could get redefined to suit an author's hypothesis. The 7 colours of the chakras don't correspond to the 7 rays of a rainbow, that's for sure.

If IsobelSeyler is allowing for a loose connection only then it could mean anything... perhaps you'll find your pot of twin-flamery at the end of the rainbow, even a twin flame.