Rainbow Rainbow in the sky

A colorful arc of colors in the sky that symbolizes hope and beauty, rainbow, legend says that there is a pot of gold in the end of a rainbow but that's just a myth. Well in reality a rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky, the color is formed because of the moisture in the air where it reflect and refract.

When can you see a rainbow?

Well mostly after a rain, but that's not the deal, a rainbow can occur when there are water drops in the air and sunlight shining from behind. Water drops mostly occur after a rain that's why rainbow usually appear after a rainbow.

Colors of rainbow

In 1672 Newton named five colors of the rainbow (Red, Yellow, Green, Blue, Violet), he later included two more colors (Orange and Indigo). But the truth is that a rainbow is composed of the entire spectrum of colors and not only that, it also include impossible colors (colors that we can't see such as red-green).

Other types of rainbow

Multiple Rainbow

Multiple or Double rainbow are caused by double reflection of sunlight inside the raindrops. Most people usually can't see them because they are fainter than the primary bow. The second bow has an inverted color (picture above).

Monochrome Rainbow

Occasionally a shower may happen at sunrise or sunset, where the shorter wavelengths like blue and green have been scattered and essentially removed from the spectrum. Further scattering may occur due to the rain, and the result can be the rare and dramatic monochrome rainbow.

Reflected Rainbow

When a rainbow appears above a body of water, two complementary mirror bows may be seen below and above the horizon, originating from different light paths. Their names are slightly different. A reflected rainbow will appear as a mirror image in the water surface below the horizon, if the surface is quiet (see photo above).

Fire Rainbow

Fire Rainbows are not rainbow or fire, they are "Halo" but mostly known as a rainbow because of its color.

Sources:
http://en.wikipedia.org/wiki/Rainbow
http://www.eo.ucar.edu/rainbows/
http://www.enotes.com/science/q-and-a/what-order-colors-rainbow-289367/