Welcome to the forum

Before setting those two up to breed, the female should be about 2 years old and the male should be at least 18 months old. While they are capable of producing young before that, the extra waiting period gives the hen time to make sure she's strong enough to lay eggs and helps to ensure that both birds are mature enough to raise chicks.
If you have a male Blue Quaker and a female Green Quaker, then all the chicks will be Green split to Blue. That means they will all look green, but carry the blue gene. If the female Green Quaker is split to Blue (and no way to visually tell, but if you know her parents you might be able to tell from that), then half the chicks will be Blue and the other half will be Green split to Blue.
Seeing as how you have a while to wait before breeding, now is the time to do lots of research into Quakers and their breeding habits. While similar to Cockatiels/Budgies, there are some things that are different.
As for general Quaker information, this forum is an excellent source for Quaker stuff