Who doesn't like rainbows? A little extra art in the sky is a good thing, isn't it? The rainbow came about because God wanted a sign to show that he would never again destroy the Earth through a flood. Genesis chapter nine speaks to its inauguration.
Gen 9:1-16 God blessed Noah and his sons, and said to them, "Be fruitful, and multiply, and replenish the earth.2 The fear of you and the dread of you will be on every animal of the earth, and on every bird of the sky. Everything that the ground teems with, and all the fish of the sea are delivered into your hand.3 Every moving thing that lives will be food for you. As the green herb, I have given everything to you.4 But flesh with the life of it, the blood of it, you shall not eat.5 I will surely require your blood of your lives. At the hand of every animal I will require it. At the hand of man, even at the hand of every man's brother, I will require the life of man.6 Whoever sheds man's blood, his blood will be shed by man, for God made man in his own image.7 Be fruitful and multiply. Bring forth abundantly in the earth, and multiply in it."8 God spoke to Noah and to his sons with him, saying,9 "As for me, behold, I establish my covenant with you, and with your offspring after you,10 and with every living creature that is with you: the birds, the livestock, and every animal of the earth with you, of all that go out of the ark, even every animal of the earth.11 I will establish my covenant with you: all flesh will not be cut off any more by the waters of the flood, neither will there ever again be a flood to destroy the earth."12 God said, "This is the token of the covenant which I make between me and you and every living creature that is with you, for perpetual generations:13 I set my rainbow in the cloud, and it will be for a sign of a covenant between me and the earth.14 It will happen, when I bring a cloud over the earth, that the rainbow will be seen in the cloud,15 and I will remember my covenant, which is between me and you and every living creature of all flesh, and the waters will no more become a flood to destroy all flesh.16 The rainbow will be in the cloud. I will look at it, that I may remember the everlasting covenant between God and every living creature of all flesh that is on the earth."WEB
I find it a little interesting that God turned the catastrophic judgement of the flood into a new covenant that was "sealed" by something so beautiful. In the case of the above picture, the rainbow actually looks like two rainbows to me, so I wonder what that means? Whatever it means, rainbows are not only beautiful, but reassuring, because God tempers wrath with beauty. And if we learn something from them along the way, so much the better!