Budgies can be easily sexed by looking at the color on their cere's once they reach adulthood. Let's start off with male Budgies, then move on to female Budgies.
Male Budgie cere's come in a variety of colors, colors like pink, blue and purple. Pink is usually found in a young male not yet 1 year old, some males however keep their pink cere's throughout adulthood, like Albino's. Here are some pictures of what a male Budgie's cere looks like.

Moving on to female Budgies, before reaching maturity they tend to have blue noses with white around the nostrils. That is how you can tell a female apart from a male while they're young. Any cere that has white around the nostrils is a female, whether the nose is pink or blue. Females can also have all white ceres, and of course the brown or tan cere. If a female's cere is crusty and brown, she's mature and ready to mate. Here are some pictures of females.

This concludes our Budgie sexing lesson! Pictures will be updated soon!