According to google colour is; “the property possessed by an object of producing different sensations on the eye as a result of the way it reflects or emits light.”
This dates to Sir Isaac Newton’s discovery in 1666 by passing a beam of light through a prism, when he was 23 years old (so what did you discover at your 23th?). He was supposedly bored during that year, he need to stay home from Uni during the plague period in Europe, so to kill some time he punched holes in the curtains of his darkened room to study the effects of light passing through a prism. The light separated into the same progression of colours found in the natural rainbow. Although Newton found the total spectrum of colours, he wanted to show that there were just seven main colours, like the seven known planets and the seven musical notes in the diatonic scale. He identified red, orange, yellow, green, blue, indigo, and violet. This was also in keeping with Aristotle's seven classes of colour which he thought were all mixes of black and white.
When do we see colour?
So even when light appears to be whit, like the sun and the light from your bedside lamp, it actually exists from the total spectrum of colours (Thanks Isaac!). But why do we some things as white and others in a colour?
Without getting to deep into the scientific aspect of colour, because it is really interesting but also a bit complicated, we start at the “see-through” light of combined colourless electromagnetic oscillations. When the colourless electromagnetic oscillations hit an object, we start seeing light. What colour light we will see is depending on which colours will be absorbed on the object true its colour molecules, and then reflects into our eyes. The colour that is absorbed is the colour that we see.
A good example is when the light hits a plant, most of the green spectrum molecules will be absorbed by the plant. This absorbed colour is reflected into our eyes and what we see is the green plant. So, we see the colour white when all the colours are reflected on the object (think of snow). We see black when all the colours are absorbed in the object. And a banana is yellow because it absorbs all the light except the red and green light, so your eye will mix the colours to yellow.
Want to know more about how the “making of colour” works in your eyes, check out this page: https://en.wikipedia.org/wiki/Color_vision#Cone_cells_in_the_human_eye Because there is more to it than the eye can see… 😊