They are actually orders that a broker is working for a customer all during the trading session. The customer gives the broker a price range and the number of shares for sale and the broker works all day to get them sold at that price. At the end of the session, if the order is complete, the broker lists it on the tape at the average price. It is a way for large sellers to hide the order size so "investors" are not scared off the ask. When the sale is green it means that the broker got his customer's orders sold at better than the closing price. When it's red, he averaged less than the closing price, it's really simple. Toxic financiers have very "special" relationships with their brokers, just as they do with the companies they finance.
During times of universal deceit, telling the truth becomes a revolutionary act -George Orwell