It depends on what sort of parakeet. There are many different types of parakeets and therefore different ways of telling the sex of it. In budgerigars (one type of parakeet) the males have a blue cere and females have a brown cere. a males nose would be a blueish-purple color and a females nose would be a light brownish-pink color
You can help the HubPages community highlight top quality content by ranking this answer up or down.