This is a basic test to find out if you or someone else is suffering from colour blindness. This free app takes one through four-five different sheets of paper where one has to read the number and match it to the two options given beneath it. At the end of the test, if all the answers are correct, you are assumed to have no problem. Wrong numbers, however, indicate that you may be having problems identifying colours. This is a basic DIY test before you run to a doctor.