Colors the the bars in a JavaFX BarChart depending upon the value of each bar's data.

colored-chart.css

/** 
 * file: colored-chart.css 
 *   Place in same directory as DynamicallyColoredBarChartWithLabel.java
 *   Ensure that the build system copies this file to the build output directory. 
 */
.root {
  -fx-not-achieved: red;
  -fx-achieved:     green;
  -fx-exceeded:      blue;
}

.default-color0.chart-bar { -fx-bar-fill: -fx-not-achieved; }
.default-color1.chart-bar { -fx-bar-fill: -fx-achieved; }
.default-color2.chart-bar { -fx-bar-fill: -fx-exceeded; }

.level-legend {
  -fx-padding: 10; 
  -fx-border-width: 2; 
  -fx-background-color: rgba(211, 211, 211, 0.5); 
  -fx-border-color: derive(rgba(211, 211, 211, 0.7), 10%);
}

DynamicallyColoredBarChartWithLabel.java

import javafx.application.Application;
import javafx.beans.value.*;
import javafx.geometry.Bounds;
import javafx.geometry.Pos;
import javafx.scene.*;
import javafx.scene.chart.*;
import javafx.scene.control.Label;
import javafx.scene.layout.*;
import javafx.scene.paint.Color;
import javafx.scene.shape.*;
import javafx.scene.text.Text;
import javafx.stage.Stage;

/** 
 * Displays a bar with a single series whose bars are different colors depending upon the bar value.
 * A custom legend is created and displayed for the bar data.
 * Bars in the chart are customized to include a text label of the bar's data value above the bar.
 */ 
public class DynamicallyColoredBarChartWithLabel extends Application {
  @Override public void start(Stage stage) {
    final CategoryAxis xAxis = new CategoryAxis();
    xAxis.setLabel("Bars");
    final NumberAxis yAxis = new NumberAxis();
    yAxis.setLabel("Value");

    final BarChart<String, Number> bc = new BarChart<>(xAxis, yAxis);
    bc.setLegendVisible(false);

    XYChart.Series series1 = new XYChart.Series();

    for (int i = 0; i < 10; i++) {
      final XYChart.Data<String, Number> data = new XYChart.Data("Value " + i, i);
      data.nodeProperty().addListener(new ChangeListener<Node>() {
        @Override public void changed(ObservableValue<? extends Node> ov, Node oldNode, final Node node) {
          if (node != null) {
            setNodeStyle(data);
            displayLabelForData(data);
          } 
        }
      });
      series1.getData().add(data);
    }
    bc.getData().add(series1);

    LevelLegend legend = new LevelLegend();
    legend.setAlignment(Pos.CENTER);

    VBox chartWithLegend = new VBox();
    chartWithLegend.getChildren().setAll(bc, legend);
    VBox.setVgrow(bc, Priority.ALWAYS);
    
    chartWithLegend.getStylesheets().add(getClass().getResource("colored-chart.css").toExternalForm());
    
    stage.setScene(new Scene(chartWithLegend));
    stage.setMinHeight(400);
    stage.setMinWidth(400);
    stage.show();
  }
  
  /** Change color of bar if value of i is <5 then red, if >5 then green if i>8 then blue */
  private void setNodeStyle(XYChart.Data<String, Number> data) {
    Node node = data.getNode();
    if (data.getYValue().intValue() > 8) {
      node.setStyle("-fx-bar-fill: -fx-exceeded;");
    } else if (data.getYValue().intValue() > 5) {
      node.setStyle("-fx-bar-fill: -fx-achieved;");
    } else {
      node.setStyle("-fx-bar-fill: -fx-not-achieved;");
    }
  }

  /** places a text label with a bar's value above a bar node for a given XYChart.Data */
  private void displayLabelForData(XYChart.Data<String, Number> data) {
    final Node node = data.getNode();
    final Text dataText = new Text(data.getYValue() + "");
    node.parentProperty().addListener(new ChangeListener<Parent>() {
      @Override public void changed(ObservableValue<? extends Parent> ov, Parent oldParent, Parent parent) {
        Group parentGroup = (Group) parent;
        parentGroup.getChildren().add(dataText);
      }
    });

    node.boundsInParentProperty().addListener(new ChangeListener<Bounds>() {
      @Override public void changed(ObservableValue<? extends Bounds> ov, Bounds oldBounds, Bounds bounds) {
        dataText.setLayoutX(
          Math.round(
            bounds.getMinX() + bounds.getWidth() / 2 - dataText.prefWidth(-1) / 2
          )
        );
        dataText.setLayoutY(
          Math.round(
            bounds.getMinY() - dataText.prefHeight(-1) * 0.5
          )
        );
      }
    });
  }
  
  /** A simple custom legend for a three valued chart. */
  class LevelLegend extends GridPane {
    LevelLegend() {
      setHgap(10);
      setVgap(10);
      addRow(0, createSymbol("-fx-exceeded"),     new Label("Exceeded"));
      addRow(1, createSymbol("-fx-achieved"),     new Label("Achieved"));
      addRow(2, createSymbol("-fx-not-achieved"), new Label("Not Achieved"));
      
      getStyleClass().add("level-legend");
    }
    
   /** Create a custom symbol for a custom chart legend with the given fillStyle style string. */
   private Node createSymbol(String fillStyle) {
      Shape symbol = new Ellipse(10, 5, 10, 5);
      symbol.setStyle("-fx-fill: " + fillStyle);
      symbol.setStroke(Color.BLACK);
      symbol.setStrokeWidth(2);
      
      return symbol;
    }
  }

  public static void main(String[] args) { launch(args); }
}