How many bands of colour are there in a rainbow?

Answer 1

there are seven colour bands in a rainbow! XX

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Normally named: red, orange, yellow, green, blue, indigo, violet - which was the description given by Isaac newton.

This is the traditional answer, but not scientifically correct.

There are no actual colour bands in a rainbow.

There is a continuous range of colours in a rainbow.

Some people seem to perceive colour bands due to their need to match what they see to what they have been taught are the names of colours.

Isaac Newton thought there should be seven colours to match up with 7 days of the week and 7 notes in the octave (A through G, the eighth note is another A) and other similar lists.

The breakdown in terms of human R,G,B vision is:

red: Red

orange: Red & Green

yellow: Red & Green

green: Green

blue: Blue

indigo: Blue, Red

violet: Blue, Red, Green

The spectrum past blue is picked up by the red and green sensing pigments in the human eye, and so it is seen as a mix of colours by humans. This is why you add red paint to blue paint to get what is seen as a colour that in reality is further away from red light than blue is.

So the trivia game answer is seven, thanks to Isaac Newton's beliefs, but the scientific reality is that these colours are just what we call things, and you could equally name them:

Red (red)

Yellow (red,green)

Green (green)

Cyan (green, blue)

Blue (blue)

Magenta (blue,red)

Which is a set of names that have common use in most representations of colour images for humans to view, such as computer displays, Photography and printing. These colours adequately represent what humans can see. These are 3 primaries for human vision, known as additive primaries (R,G,B) because you can add them together to get white light, and the 3 subtractive primaries (C,M,Y), which can be used to take colours out of white light to get black.