My son says everything is black, gray and white. He only identifies these 3 colours. How can I tell if he is telling the truth or just lying? Does he need a doctor or some help?

How old is he? in the initial months babies are not able to identify all colours. however, if ur baby is more than a year n half old, he should be able to start identifying different colours. start showing different toys with different colours. keep repeating the name of colours. later, see if ur kid can remember and identify. if you don't see a change do speak to the doc