We said earlier that because the eye only registers relative amounts of red, green and blue it is sufficient when taking a photograph to only record the amount of each of those colours at each point in the image. The image can then be thought of as made up of three superimposed components, one for each primary colour. The components are sometimes called channels.
Here are some examples of images from our site showing the intensity in each channel. The top row is the red channel, the second green, and the third blue. You should be able to see that the channel you would expect is brightest for each image. It is interesting though that blue sky has a considerable amount of red and green in it. This means that the blue of the sky is not nearly as saturated a colour as the red of the tomato.