Most buds are sold ASAP from harvest, but previous to the retail mindset- we only had green buds after the fall harvest until about Christmas.
The pot shops have made an art of creating an image of what a bud should look like, which go far beyond curing-when you are trying to remove chlorophyl as the plant is still alive.
The marketing machine will remove air and inject Nitrogen into the packaging to keep that "fresh" green look. (it's a good practice to check the harvest date)
Unfortunately, people associate brown buds with the old brick weed which was left out in the fields to dry before curing was more common.