I have tried lots of things from putting more lime juice in to keeping the pit of the avocado in the bowl when stored but nothing really worked. The guacamole always turned an unappetizing brownish color. I have found a better way to store guacamole.  Next time, place the guacamole in an airtight container. Pat the guac down with a spoon so it is flat and smooth on top. Now, add a tiny amount of water. I’m talking only about 1/2 an inch on the top. Place the lid on the storage container and place in the fridge. Now your guacamole will stay fresh and most of all GREEN! When you are ready to eat it again, simply drain off the excess water, stir and enjoy.