Colours

​ ​Colors. Imagine how boring the world would be without them. What are colors really and where are they all coming from? ​ ​Ordinary white light is carrying a secret. It is not at all white, as it looks. Instead, white light consists of a mixture of light beams of all the colors of the rainbow.

When we see all those colors together we perceive them as white light. But what it really is, is a bunch of colors at the same time, all jumbled up. Sometimes, nature happens to reveal this secret. If you have the sun in your back, and you look towards a place where it is raining, then you'll see a rainbow. The white light from the sun hits the rain drops in the air and is dispersed in it's constituting colors, neatly sorted. ​ ​At the top, the light is red. That is gradually merged into orange and then yellow, which becomes increasingly green, then blue until you reach the lowest inner most part of the rainbow that is violet, before the colors fade away again.

One often hears that the rainbow has seven colors: red, orange, yellow, green, blue, indigo, violet. Roy G. Biv, is a mnemonic to memorize that list. But if you look carefully, you see that the colors shift gradually and that there is no clear number of colors. Most of the time we see no rainbow at all.

The sun shines with all its colors mixed together as white light. When the white light hits something and is reflected, that's when interesting things start to happen. ​ ​Here comes white light, a bunch of light beams of various colors that is, and hit a yellow shirt. Some of the colors are soaked up by the shirt. They are absorbed. The other colors are reflected, travels onward and hits our eyes.

The eyes and brain then interpret this combination of colors so that we perceive it as yellow. This is what makes a yellow shirt appear yellow. The fabric absorbs all colors except those that we interpret as yellow. To say that something is of some color is the same thing as saying that it absorbs all light beams except those of that color. But wait a moment.

Where do those light beams go, those which are absorbed? They turn into heat. You can notice this if you are wearing a black shirt on a sunny day. ​ ​A black shirt absorbs all colors and reflects almost no light at all. Because of that, a black surface is heated more by the sun than a white. White clothes reflect all colors and thus absorb less sunlight.

That is why it feels good to wear white on a hot and sunny day. ​ ​Paint contains small particles - pigments - which are mixed in the paint because they absorb some color tones and reflect the rest. Here is a paint that absorbs all red tones. The light beams that are reflected then - mostly blue and green tones - are interpreted by our eyes and brains as cyan blue. Here is a paint that absorbs all mid-blue tones. The colors reflected from it then we interpret as yellow.

If we mix these two paints we get one that absorbs both red and blue. The remaining color tones being reflected is interpreted by our eyes and brains as green. For each new pigment you mix in, another color is subtracted away from the resulting spectrum. This is a color mixing scheme to use when you mix paint. Each color of paint subtracts some color tones from the light as the pigment absorbs them.

But when you mix using colored light, you add colors for each new light you turn on. This is a color mixing scheme to use when you mix light. Colored light adds tints. If you mix all colors of the rainbow with paint, you get close to black. But if you mix them using light, you get white.