They may not eata lot of it if they are finding enough in their environment, but I always make sure that it is available. It used to only be sold in 50 pound bags, but now they are available in smaller ones for pretty much the same price, LOL. It does last a long time.
The poop is green because of bile excreted by the liver. If they are not eating a lot, the poop is darker green. The above poop is a little runny, but not that bad.
I usually feed 20% flock raiser or all flock feed, but when I have used layer feed, it is 16%. When you have birds who may no longer lay eggs, chicks and young pullets, or roosters and cockerels, they don’t need all of the calcium that layer feed has. So that is when 20% all flock is best. They like it better too. If using all flock I do keep a container of crushed oyster shell available for the layers, just like grit, in separate pans from feed.