From below given colours, which colour is not present in 7 colours of rainbow?
A. Violet
B. Purple
C. Green
D. Indigo

Hint: This is a question based on common everyday observations. Remember the colours of a rainbow and write them down in an order. You can remember the colours of a rainbow through a slang like “vibgyor” which denotes the initials of all the colours in a rainbow. This will help you to eliminate the wrong options.

Complete Step-by-Step solution:
Rainbows arise in seven colors, as water droplets divide the sunlight into the spectrum's seven colors. If sunlight travels through a prism you get the same effect.

The colors of the rainbow are:
1. Red
2. Orange
3. Yellow
4. Green
5. Blue
6. Indigo
7. Violet
We can see “Violet”, “Green”, and “Indigo” are the colors of a rainbow.
Thus option B “Purple” is the correct answer to the problem.

Note: Sunlight and environmental conditions produce a rainbow. The atmospheric water droplets function as prisms though the traces of light are quite complicated. Once light reaches a droplet of water, it is refracted at the border of air and water and reaches the droplet, where the light is distributed through the seven colors. The light reflects the droplet's within, splitting into wavelengths — or colors of its component. The rainbow effect takes place as the light is first reflected throughout the droplet and then reflected back into the air again. As light exits one medium and reaches another, the light switches and shifts the path of propagation. It is regarded as refraction. Since of refractive index variations, though, this angle of refraction differs with each color or according to the light's wavelength. This shift in the refraction angle, or refractive index, is called dispersion according to the wavelength of light.