A rainbow forms when each tiny droplet of water disperses sunlight. The pattern of light is always the same in a primary rainbow because each color is reflected at its own particular wavelength. In a primary rainbow, the colors will be in the order of red, orange, yellow, green, blue, indigo and violet. Or ROYGBIV. read more
In addition to the common primary and secondary rainbows, it is also possible for rainbows of higher orders to form. The order of a rainbow is determined by the number of light reflections inside the water droplets that create it: One reflection results in the first-order or primary rainbow; two reflections create the second-order or secondary rainbow. read more
The order of colors in a rainbow is easiest to remember by the following mnemonic (a formula that helps one remember something): ROY G. BIV. R=red, O=orange, Y=yellow, G=green, B=blue, I = indigo, and V=violet. Red is at the top edge of the rainbow and violet is at the bottom edge, with the other colors in between. read more