We tried to do addition of the colors of light in the previous stage.
Well, what will happen if subtraction is done?
・ A transparent pet bottle
（The label on the side was removed）
・ Water and a little milk
・ A flashlight
Ａ．Fill the bottle with water and add a little milk.
（For every 1.5 liters of water add a little under 1 milliliter of milk）
Ｂ．Put on the cap and shake the bottle until the liguids are mixed.
Ｃ．In a darkened room shine the flashlight through the botton of the horizontal bottle as seen in the photograph.
Ｄ．View the bottle from the side.
How does the color of the light seen?
Ｅ．Next view it from the mouth of the bottle.
Ｆ．Change the amount of milk, and try it when it seems bad.
It fails when there is too much milk.
It seems to be an orange color when it is seen from the mouth.
It seems just a little bluish when it is seen from the side.
Light is equal to dust and the little molecular particles of the air, and the phenomenon in which that proceeding direction is changed is said to be the dispersion of the light.
Then, it has the nature that it is often scattered mostly as blue light.Therefore it seems that the sky is blue in the daytime when it is fine.
On the other hand, when the direction of the sun is seen in the evening, it seems that the sky is reddish by the sunset glow. Because the light proceeds obliquely through the class of air whose light in this case is thin, it passes a very long distance, and is scattered here and there, and the light which remains is red because that is how light looks to our eyes when it is lacking blue or purple light.
In other words,
white-blue, purple = orange color.