Which one of the following colours is not a part of the rainbow

Correct option is B

The correct answer is: (b), Grey
A rainbow, a common atmospheric optical phenomenon, forms as a multicolored arc in the sky when sunlight interacts with water droplets, causing them to refract sunlight. This refraction separates the sunlight into its constituent colors, each reflecting at different angles due to their varying wavelengths. Rainbows can also be observed in other conditions, such as fog, sea spray, or near waterfalls.
Despite its appearance, a rainbow is an optical illusion and does not have a physical presence in any specific spot in the sky. It is the result of both refraction and reflection of light. Refraction involves a change in the direction of a wave, making it appear "bent," while reflection causes waves to "bounce back" from surfaces or wavefronts.
The colors of a primary rainbow always appear in a specific order dictated by their wavelengths, ranging from longest to shortest: red, orange, yellow, green, blue, indigo, and violet.