Vary symbology by color

Varying the color of symbols along a color scheme is a good way to indicate quantitative variations of an attribute. For example, point symbols representing observation stations can be colored along a diverging red-blue color scheme to show relative temperature recordings. Variations in color of line symbols representing roads can indicate traffic volume or speed.

This 3D scene of New York City uses a scientific color scheme as a visual variable to highlight taller buildings.

The simplest way to vary symbol color is to set the layer symbology to one of the color-based layer symbology options. Unique values assigns a different color to unique instances of the specified attribute field. You can customize this by modifying each symbol and adding to, combining, or removing values. Graduated colors classifies qualitative differences with a discrete number of symbol colors. Unclassed colors shows variation in a feature attribute by distributing a color scheme evenly across features. Or, you can refine one of the size-based layer symbology options by setting the color variable to a field or an expression. In addition, you can control the color of symbol layer properties by connecting them to a field of hexadecimal color values. While theoretically you can use more than one of these approaches together on a single layer, be aware that the result may be too complex to be understandable. Use these techniques judiciously.

Learn more about layer symbology

Learn more about symbol properties to attributes

Set the color variable to a field or an expression

When a layer is symbolized with single symbol, unique values, graduated symbols, or proportional symbology, you can also vary the color of the symbols. You can set the color variable to a numeric attribute field or write an expression. The attribute can be the same or different than the one used by the layer symbology. Choose a color scheme to apply to the range of values.

For example, a layer of points representing earthquakes drawn with graduated symbols shows classified circles sized relative to the earthquake's magnitude. The color variable set to a numeric field indicating damage displays the degree of damage for each circle based on colors along a specified color scheme.

Note:

When working with the color variable on polygon features, the color is applied to the template (point) symbol, not the background (polygon) symbol.

To set the color variable to a field or an expression, complete the following steps:

1. Select the feature layer in the Contents pane.
2. On the Feature Layer tab, in the Drawing group, click Symbology .
3. In the Symbology pane, on the Vary symbology by attribute tab , expand the Color heading and do one of the following:
   • Choose a numeric field from the Field menu to vary the symbol color.
   • Write an expression to determine color values. Choose Custom from the Field menu, or click the Set an expression button to open the Expression Builder dialog box. Write an expression and click Verify to validate it. Note that although an expression is valid, it may not return a valid numeric value for the color variable. You can filter the Expression Builder dialog box to show only numeric fields to help prevent this.

     Learn more about writing expressions in the Arcade language

4. Optionally, choose a Normalization field. Normalization is not available when the color variable is set to an expression.
5. Select a color scheme.

   When symbolizing polygon feature layers, you can modify the color of the polygon symbol fills or outlines (or both) by the color scheme. Click the Color scheme options button to choose the target for the color scheme. The target determines which symbol layers (fill symbol layers and stroke symbol layers) of the symbol are affected. Symbol layers that are color locked are not updated by changes to the color scheme regardless of the color scheme target setting.

6. Optionally, adjust the histogram values. See Histograms for more information.

   If the source data has changed or been updated, click Refresh values to update the range of values.

7. Check the Show legend check box to add a representation of the color variation to the layer's legend in both the Contents pane and any legends placed on layouts.
8. To remove the color variable or the normalization field, choose <none> from the Field or Normalization menus.

Caution:

• Expressions are not saved by the layer if you change the color variable to read from a field instead of an expression. You can save the expression from the Expression Builder dialog box by clicking Export before making changes.
• If you share a point feature layer that uses a color variable, be aware that any point symbol other than a simple circle or square will be downgraded to a circle in the resulting web map.

Classify unique value categories by color

When a feature layer is symbolized with unique values symbology and a variable is applied to vary the symbology by color, you can classify the variable to symbolize both a category and a quantity with one layer. For example, you may display a road network using a categorical field to represent the type of road, and vary the symbology with a numeric field representing the traffic volume.

The symbology's legend shows the name of the field or expression and the classified unique value categories' default symbols. This is followed by the name of the field or expression used to vary the symbology, and a legend patch for each class symbol's color. Use the Show expanded legend option to show the resulting symbols for every unique value class.

Classifying your data this way allows you to display more information. However, it also adds complexity to the map and its legend, especially if other layers in the map are symbolized in the same manner.

To classify the color variable, follow the steps below.

1. Ensure your feature layer is set to use unique values symbology.
2. Follow steps 1 through 3 in the above section to set a color variable to a field or expression.
3. Turn on the Classify data toggle button.
4. Optionally, choose a classification method and set the number of desired classes.
5. Choose a color scheme, or click the Classes and Histogram tabs to adjust the color values of each class and view the distribution of the data in the field.
   • Optionally, click the Color scheme options button to choose the target for the color scheme.
   • Additionally, you can select the Overwrite all color attributes option to overwrite the color attributes set by the color scheme, or the Preserve hues only option, which only overwrites the color's saturation and value.