I was really praying that the rainbow I saw on the way to work today meant I would find a pot of gold in the middle of the expressway! But when I got closer, the rainbow moved and disappeared... and I didn't see a pot of gold anywhere.
I still looked up rainbows when I got to work to see if it was good luck anyway. Turns out, the pot of gold myth isn't REALLY about literal riches... it's about fertility. There was a Celtic superstition that making love under a rainbow would insure a successful pregnancy... to them, the pot at the end of the rainbow represented a woman/womb and the gold inside symbolized children!
In many other cultures and faiths, rainbows represent beauty, good luck, creation and enlightenment. And in the bible, references to rainbows are often interpreted as a sign of God's promise for the future and His reconciliation with mankind.
Sounds like good luck to me!