How to tell when pork shoulder is done?

I am making bbq sandwiches in my crockpot. I put the pork shoulder in the crock pot with spices and water at 6am this morning. It is now almost 4pm and I don't think it is done. I checked it and it feel apart but it is all pinkish purple color. I ume that means it is not done lol. How much longer should I cook it? If I can't use it tonight is it ok to let it cool and put it in the fridge for tomorrow? Thanks for the help.