Experimental evidence has shown that for the human eye to feel white, it is not necessary for all the colors of the rainbow to reach it.
If red, blue, and green lights simultaneously hit our eyes, that will be enough to cause the visual sensation of white light.
When two of these three colored lights - red, blue, and green - simultaneously strike the human eye, they cause visual sensations that, oddly enough, are not the same as those caused by the separate lights.
red light + green light = visual sensation of yellow
red light + blue light = visual sensation of margenta
green light + blue light = cyan visual sensation.
The color of objects
The color a body displays when illuminated depends on the kind of light it diffusely reflects. White light consists of a multitude of colors that can be divided into seven colors: red, orange, yellow, green, blue, indigo and violet.
An observer sees each body with a certain color, as follows: if the light incident on the body is white (composed of all colors) and the body absorbs the full range of colors, reflecting only blue, the body is blue . So the white body is one that diffusely reflects all incident white light and the black body is one that absorbs all colors, diffusely reflecting no color.
The colors of tv and computer monitors
The television picture tube is an example of a light source. The light rays produced by this source leave the device through the screen and reach the human eye. A color television screen can produce a large number of different colors using only the three primary colors of light: red, green and blue.
This canvas consists of a large number of small fillets of these three colors, interspersed. The device works to illuminate these fillets with more or less intensity and thus compose the various colors we can see on the screen.
In a region where the fillets of all three colors are fully lit, we see white. Where everyone is blacked out is black. If only the green and red fillets are lit, you have the visual sensation of yellow. And so on.
Take a close look at the screen of a working color TV and you will notice the existence of these small structures with the primary colors.
Color computer monitors work similarly. In fact, on both color television and color computer monitors only three colored lights are present.