I would be more concerned if there were a few million shares on level 2 on the bid with zero volume. That scenario means everyone wants to sell but nobody wants to buy. This is not the case. It's simply weak hands selling off for whatever reason.
All actual trades end in buys. If shares are bought on the bid they appear as a sell(red). If they are bought on the ask they appear as a buy(green). If bought in between they appear as unknown(black/?). There basically cannot be a trade that doesn't end as a buy.