How does the Historical Put/Call Ratio Chart work?
By overlaying the underlying stock chart, we are able to see correlations between peaks in the stock chart, (and subsequent drops), and high put/call ratios.
The legend has call options in green that are displayed as negative value bars on the chart. This shows correlations with the underlying stock price. When the put/call ratio is high (ie, there are many more put options than call options), we want the chart to be positive.
You can see a similar chart with the insider sell/buy ratio charts on this page: https://fintel.io/macro