A baby who first habituates to a green circle and then recovers to a blue circle can distinguish between green and blue.
Habituation refers to a type of non-associative learning in which an innate response to a stimulus is reduced after repeated or prolonged presentations of that stimulus. So, according to this definition, in the example provided, the baby habituates to the green circle so he reduces his interest in it and recovers to a blue circle since it is a new stimulus to him.