Perhaps you can relate to the following scene: I'm driving along, with my kids in the back seat, and suddenly, I spot a rainbow. I make a point of saying something to my sons and daughter, so they won't miss it. "Look, a rainbow!" About the same thing I do with we drive by something else I'd like to point out, like cows or fire trucks.
Only thing is, there is something different about a rainbow, something which separates it from cows and other attractions.
Genesis 9:14-15 "And it shall be, when I bring a cloud over the earth, that the rainbow
shall be seen in the cloud. And I will remember My covenant which is between Me and you and every
living creature of all flesh; and the waters shall no more become a flood to destroy all flesh."
God looked at the destruction, which He had sent as a way of dealing with the sin of the world, and said to Himself that He needed to find another way to deal with it. He would send His only begotten Son, to become a sacrifice for our sin, so that you and I would not have to go through the same kind of destruction that had just been visited upon the world.
The Rainbow is a reminder to you and me of what Jesus did on the Cross. Even though you and I are staring death in the face, because of sin, we've been given a pardon. We've been rescued. When you see a rainbow, think of it as much more than a trick the sunlight plays on airborne water particles. It's there to bring to mind for us Who God is, what He did, and who we are in Him.