For every sell there is a buy an the green on my screen today indicates a lot of buys at the bid.
Every transaction is a buy and a sell. If a transaction occurs at Bid it is classified as a sell. If the transaction occurs at Ask it is classified as a Buy. A transaction at Bid can not be classified as a buy.
The reason markets track true Buy and Sell actions is to determine if the market is bullish or bearish. Since most transactions occurred at bid the market reflects bearish on the buy sell indicator.