I have two parakeets and i need to know the genders?

ok i got two parakeets a couple weeks back and i want to know the of them one of them is yellow with a gray belly and with black markings on the head and its cere its kinda white and the ohter one is blue and white with black markings and it just grew some dark blue flecks on the side of its face and its cere is pinkish-purple with light blue on the edge. whats their gender because i want to breed them(i know who to take care of the babies you feed them every 5 minutes)oh and their still kinda young(thats what the lady at petsmart said anyway)