Yes, it is possible for a toddler to be color blind. And color blindness is more common in boys but rare in girls. They can be inherited from parents. If you or your families have color blindness, your son is likely to get color blindness since he has problems in telling colors. So, you'd better take him to eye doctor for an eye examination to make sure if he suffers color blindness.
In most cases, color blind is hereditary. So if there is one in your husband and your family is colorblind, it's a lot more likely that your child is color blind. But it is quite normal for a 3 year old having problems in telling colors because the names of colors are actually quite arbitrary. If you are not sure, you can take him to have an eye test.
Yes. It is possible. But your son is just 3 years old, so maybe he is just confused about colors, you can teach him with more patient. If he still has problem in telling colors, you can get him some test or take him to see a doctor to make sure if he is color blind. If it is do, don't worry. Nowadays, there are a lot of ways to solve this problem. such as color blindness corrective morrors.