change tooltip color in amchart

I want to change the background colour of the tooltip value in Amchart 5. I mean the black background colour.

Solution

You can create an instance of Tooltip and store it in a variable. Use it in your valueAxis configuration, then modify the background color of your tooltip through its background element.

let tooltip = am5.Tooltip.new(root, {});
  
let valueAxis = mainPanel.yAxes.push(
  am5xy.ValueAxis.new(root, {
    // ...
    tooltip,
    // ...
  })
);

tooltip.get("background").set("fill", am5.color(0x0000ff));

Full example (using this demo from the official website):

am5.ready(function() {

  // Create root element
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/getting-started/#Root_element
  let root = am5.Root.new("chartdiv");

  // Set themes
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/concepts/themes/
  root.setThemes([am5themes_Animated.new(root)]);

  // Create a stock chart
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/stock-chart/#Instantiating_the_chart
  let stockChart = root.container.children.push(
    am5stock.StockChart.new(root, {})
  );

  // Set global number format
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/concepts/formatters/formatting-numbers/
  root.numberFormatter.set("numberFormat", "#,###.00");

  // Create a main stock panel (chart)
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/stock-chart/#Adding_panels
  let mainPanel = stockChart.panels.push(
    am5stock.StockPanel.new(root, {
      wheelY: "zoomX",
      panX: true,
      panY: true
    })
  );

  // Create value axis
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/xy-chart/axes/
  let tooltip = am5.Tooltip.new(root, {});
  
  let valueAxis = mainPanel.yAxes.push(
    am5xy.ValueAxis.new(root, {
      renderer: am5xy.AxisRendererY.new(root, {
        pan: "zoom"
      }),
      extraMin: 0.1, // adds some space for for main series
      tooltip,
      numberFormat: "#,###.00",
      extraTooltipPrecision: 2
    })
  );

  tooltip.get("background").set("fill", am5.color(0x0000ff));

  let dateAxis = mainPanel.xAxes.push(
    am5xy.GaplessDateAxis.new(root, {
      baseInterval: {
        timeUnit: "minute",
        count: 1
      },
      renderer: am5xy.AxisRendererX.new(root, {}),
      tooltip: am5.Tooltip.new(root, {})
    })
  );

  // add range which will show current value
  let currentValueDataItem = valueAxis.createAxisRange(valueAxis.makeDataItem({ value: 0 }));
  let currentLabel = currentValueDataItem.get("label");
  if (currentLabel) {
    currentLabel.setAll({
      fill: am5.color(0xffffff),
      background: am5.Rectangle.new(root, { fill: am5.color(0x000000) })
    })
  }

  let currentGrid = currentValueDataItem.get("grid");
  if (currentGrid) {
    currentGrid.setAll({ strokeOpacity: 0.5, strokeDasharray: [2, 5] });
  }


  // Add series
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/xy-chart/series/
  let valueSeries = mainPanel.series.push(
    am5xy.CandlestickSeries.new(root, {
      name: "AMCH",
      clustered: false,
      valueXField: "Date",
      valueYField: "Close",
      highValueYField: "High",
      lowValueYField: "Low",
      openValueYField: "Open",
      calculateAggregates: true,
      xAxis: dateAxis,
      yAxis: valueAxis,
      legendValueText:
        "open: [bold]{openValueY}[/] high: [bold]{highValueY}[/] low: [bold]{lowValueY}[/] close: [bold]{valueY}[/]",
      legendRangeValueText: ""
    })
  );

  // Set main value series
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/stock-chart/#Setting_main_series
  stockChart.set("stockSeries", valueSeries);

  // Add a stock legend
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/stock-chart/stock-legend/
  let valueLegend = mainPanel.plotContainer.children.push(
    am5stock.StockLegend.new(root, {
      stockChart: stockChart
    })
  );

  // Set main series
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/stock-chart/#Setting_main_series
  valueLegend.data.setAll([valueSeries]);

  // Add cursor(s)
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/xy-chart/cursor/
  mainPanel.set(
    "cursor",
    am5xy.XYCursor.new(root, {
      yAxis: valueAxis,
      xAxis: dateAxis,
      snapToSeries: [valueSeries],
      snapToSeriesBy: "y!"
    })
  );

  // Add scrollbar
  // -------------------------------------------------------------------------------
  // https://www.amcharts.com/docs/v5/charts/xy-chart/scrollbars/
  let scrollbar = mainPanel.set(
    "scrollbarX",
    am5xy.XYChartScrollbar.new(root, {
      orientation: "horizontal",
      height: 50
    })
  );
  stockChart.toolsContainer.children.push(scrollbar);

  let sbDateAxis = scrollbar.chart.xAxes.push(
    am5xy.GaplessDateAxis.new(root, {
      baseInterval: {
        timeUnit: "minute",
        count: 1
      },
      renderer: am5xy.AxisRendererX.new(root, {})
    })
  );

  let sbValueAxis = scrollbar.chart.yAxes.push(
    am5xy.ValueAxis.new(root, {
      renderer: am5xy.AxisRendererY.new(root, {})
    })
  );

  let sbSeries = scrollbar.chart.series.push(
    am5xy.LineSeries.new(root, {
      valueYField: "Close",
      valueXField: "Date",
      xAxis: sbDateAxis,
      yAxis: sbValueAxis
    })
  );

  sbSeries.fills.template.setAll({
    visible: true,
    fillOpacity: 0.3
  });

  // Data generator
  let firstDate = new Date();
  let lastDate;
  let value = 1200;

  // data
  function generateChartData() {
    let chartData = [];

    for (var i = 0; i < 50; i++) {
      let newDate = new Date(firstDate);
      newDate.setMinutes(newDate.getMinutes() - i);

      value += Math.round((Math.random() < 0.49 ? 1 : -1) * Math.random() * 10);

      let open = value + Math.round(Math.random() * 16 - 8);
      let low = Math.min(value, open) - Math.round(Math.random() * 5);
      let high = Math.max(value, open) + Math.round(Math.random() * 5);

      chartData.unshift({
        Date: newDate.getTime(),
        Close: value,
        Open: open,
        Low: low,
        High: high
      });

      lastDate = newDate;
    }
    return chartData;
  }

  let data = generateChartData();

  // set data to all series
  valueSeries.data.setAll(data);
  sbSeries.data.setAll(data);

  // update data
  let previousDate;

  setInterval(function() {
    let valueSeries = stockChart.get("stockSeries");
    let date = Date.now();
    let lastDataObject = valueSeries.data.getIndex(valueSeries.data.length - 1);
    if (lastDataObject) {
      let previousDate = lastDataObject.Date;
      let previousValue = lastDataObject.Close;

      value = am5.math.round(previousValue + (Math.random() < 0.5 ? 1 : -1) * Math.random() * 2, 2);

      let high = lastDataObject.High;
      let low = lastDataObject.Low;
      let open = lastDataObject.Open;

      if (am5.time.checkChange(date, previousDate, "minute")) {
        open = value;
        high = value;
        low = value;

        let dObj1 = {
          Date: date,
          Close: value,
          Open: value,
          Low: value,
          High: value
        };

        valueSeries.data.push(dObj1);
        sbSeries.data.push(dObj1);
        previousDate = date;
      } else {
        if (value > high) {
          high = value;
        }

        if (value < low) {
          low = value;
        }

        let dObj2 = {
          Date: date,
          Close: value,
          Open: open,
          Low: low,
          High: high
        };

        valueSeries.data.setIndex(valueSeries.data.length - 1, dObj2);
        sbSeries.data.setIndex(sbSeries.data.length - 1, dObj2);
      }
      // update current value
      if (currentLabel) {
        currentValueDataItem.animate({ key: "value", to: value, duration: 500, easing: am5.ease.out(am5.ease.cubic) });
        currentLabel.set("text", stockChart.getNumberFormatter().format(value));
        let bg = currentLabel.get("background");
        if (bg) {
            if(value < open){      
              bg.set("fill", root.interfaceColors.get("negative"));
            }
            else{
              bg.set("fill", root.interfaceColors.get("positive"));
            }
        }
      }
    }
  }, 1000);

}); // end am5.ready()

#chartdiv {
  width: 100%;
  height: 350px;
}

<script src="https://cdn.amcharts.com/lib/5/index.js"></script>
<script src="https://cdn.amcharts.com/lib/5/xy.js"></script>
<script src="https://cdn.amcharts.com/lib/5/stock.js"></script>
<script src="https://cdn.amcharts.com/lib/5/themes/Animated.js"></script>

<div id="chartdiv"></div>