Interface PointFigureColumn

Border colour for this bar alone, on the same terms as wickColor.

Per-bar colour override, honoured by every Family-A renderer: candles and OHLC bars take it on body, border and wick together, histogram and column on the bar, and line, step, area and the HLC-area close line split their stroke into runs at the bars where it changes. Baseline is the exception, its stroke is already split by the above/below-base rule. A MACD histogram is four colours by momentum, and a conditional study is two. Neither is expressible with one colour for the whole series.

Open interest: contracts outstanding at the end of this bar. Optional, because only a derivatives feed carries it; on a cash instrument it is absent, and absent is not zero. Zero is a real reading on a contract nobody holds.

It is a level, not a flow, and that is the whole reason it needs saying here. Volume is a quantity traded during the bar, so folding five one-minute bars into a five-minute bar adds five volumes together. Open interest is a position as at the bar, so the same fold takes the last one and adding them would produce a number five times too large that still looks entirely plausible on a chart.

Every aggregation path in this library therefore treats the two differently: mergeBars, the higher-timeframe fold in securitySeries, and the tick-to-bar builders all sum volume and carry the latest open interest. A transform that maps one source bar to one output bar passes it through; one that invents bars from price alone (Renko, Point and Figure) does not carry it at all, because a synthetic bar has no instant to be the position as at.

Wick colour for this bar alone, over color. A study that paints candles with a translucent body and a solid wick cannot say so with one colour, and without this a per-bar override always set the two together. Read by the candle renderers only; absent means the wick follows color.