White light consists of the visible light colors in the electromagnetic spectrum. The electromagnetic spectrum consists of waves of different wavelengths. The seven colors that are visible to humans have different wavelengths. Red has the highest wavelength, then orange, yellow, green, blue, indigo and finally violet, which has the shortest wavelength.
Even though all colors have different wavelengths, they all travel at the same velocity, the speed of light. Due to the difference in wavelength, every time light enters a medium of different density, the colors bend differently and split to form a rainbow pattern. This process of bending when white light moves from one medium into another is called refraction. For example, when white light travelling through air enters either glass (such as a prism) or water (such as rain drops), the violet component bends more than the rest of the colors and red bends the least, thus splitting the light into the seven colors of the rainbow.
Even though white light can be split into seven colors, only three colors of light are required to combine and give white light. These colors – red, blue and green – are known as the primary colors of light. All other colors can be obtained by combining the primary colors in different proportions.Learn more about Colors