gridView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView parent, View view, int position, long id) {
                view.setBackgroundColor(...);
                return true;
            }
        });

for (int i=0;i < arg0.getChildCount();i++){

                if (position==i){
                    v.setBackgroundColor();
                }else{
                    v.setBackgroundColor();
                }
            }