What causes an object to look red or green, etc?

What causes an object to look red or green, etc?

PROF WAQAR HUSSAIN

         When light falls on a red object, it absorbs all radiations except red. So red wavelength is reflected back and the thing appears red. For example, a tomato looks red as it absorbs all wavelengths of colours i.e. violet, indigo, blue, green, yellow and orange except red and thus red is reflected and tomato appears red.

          Similarly a green chilli absorbs all the colours except the green which is reflected back and it appears green. So you can make a general formula that the colour of the thing is the colour it is reflecting.