Your baby is just 4 months now, but it so amazing that he knows colors like you and me. Your baby's brain works in such a way that he easily recognizes colors, even though there is much time before he spells it loud and clear.
What you need to know
It has been found through experiments that babies at this age, if shown bright colors, are capable of distinguishing them without any confusion. This is one of the reason why it is said that you must introduce bright colors from an early age.
Babies develop a fancy for colors much before they develop speech. This is why most of us are unaware about this fascinating fact about babies.
Bring in a lot of bright colors in your baby's life to improve his perception of colors. This will improve his vision and at the same time make him feel happy.