The discovery of the colors of the rainbow is attributed to Sir Isaac Newton, an English physicist and mathematician. In the late 17th century, Newton conducted a series of experiments with light, specifically passing a beam of sunlight through a glass prism. He observed that the prism separated the white light into a spectrum of colors - red, orange, yellow, green, blue, indigo, and violet. This experiment led Newton to understand that white light is composed of different wavelengths of light, each corresponding to a different color. So, we credit Sir Isaac Newton with the discovery of the rainbow colors.