Do you known why an apple or tomato appears red the grass green and the milk white when they are all illuminated by the sunlight have you wondered why in the dark all objects look black? In face the color of objects depends upon the color it reflects.
The sunlight which appears to be white actually comprises seven colors- violet, indigo, blue, green, yellow, orange, and red. In sunlight an apple or tomato appears red because it reflects only the red component of light and absorbs the test. Grass appears green because it reflects only the green color and absorbs all other colors present in the sunlight. A white shirt or milk appears white because it reflects all the color of the sunlight. And a black board appears black because it absorbs all the colors of white light and reflects none.
To prove this phenomenon focus red light on a white shirt and you will see that it becomes red. White objects take the color of light falling on it. Similarly if we see an apple in red or white light it will appear red but in green or blue light it would appear black. It cannot reflect any other color but red and therefore looks white. This is how the various objects get their color.