I cook them with a little salt in the water with several cloves of peeled garlic for about 15-20min until tender,then drain off the water and add a little real butter.Young tender ones usually stay green,but if they are getting old sometimes they turn a greenish brown color.

~Molɔ̀ːn Labé Skýla~
As Bob Hagel would say"You should not use a rifle that will kill an animal when everything goes right; you should use one that will do the job when everything goes wrong."Good words of wisdom...............