large black dots ..............small hive beetles
small black dots...............mites
yellow and brown dots......wax cappings from the honey stores they are eating
white dots......................not sure, are you feeding dry sugar? or it could be snow pellets
dead bees are just part of the winter thing, some go out on cleansing flights and get too cold to make it back in, others are old and weak, while some will die in the hive and are taken out by others.
Bee poop on the side of the hive is a sign they are taking cleansing flights.