Identifying and noticing different colours needs the accurate development of two things – your baby’s sensory development, that will pick up the right colour tone and your baby’s cognitive brain development, that will process all the information.
Your baby will start identifying colours, different shapes, sizes, and geometric patterns around the same time – sometime around the 18th month. It will take a while before he/she knows the basic colours. Most children can name at least one by 36 months. Your child’s playschool would help him in this regard.
Parents can also encourage their children to pick up the names of the different colours by using the names of colours in daily conversation with their baby. For instance, say “red flower” or “blue shirt” and then correspondingly point towards that object so that your child can both see the object in question and as well as hear the colour words you are describing to identify that object.
You can also play different colour games with your baby like matching colours (where you tell your child to choose different items of the same colour), colour pointing games (ask your child to point towards the colour you name), and colour naming games (a late-stage game where you try to make your child memorize and select different colours at random).
Please remember that kids always learn new things at their own pace. Do not fret or be unnecessarily worried if unlike other children, your child is being unable to process or memorize colour names or is simply disinterested.
You should consult a doctor, only if you see your child failing at identifying colours repeatedly over a long period of time. If you suspect a problem, talk to your child’s doctor or contact an ophthalmologist to get your child tested for colour blindness, a problem in which one cannot distinguish between certain colours.