Customizing the colormap presets in Grapher

Colormaps are an important tool in illustrating complex scientific information.  Grapher comes with a variety of predefined colormaps including several rainbow, gradient, divergent, and discrete styles. If the predefined colormaps do not meet your needs, you can customize them or create brand new ones using the Colormap Editor.

This article covers the following topics:

Creating custom colormaps

The easiest way to create a custom colormap is to start with a similar pre-existing one.  To do this:

1. Open the Colormap Editor: 
   • From a Bubble plot or Bar graph, click the Fill tab in the Property Manager window, set the Color method to Numeric via colormap and set the variable (or set the Color method in Grapher 26 and previous versions), and then click the Custom colormap (...) button.
   • From a Scatter plot or Line plot, click the Symbol tab in the Property Manager window, set the Color method to a variable, and then click the Custom colormap (...) button.
2. Click in the Presets field and select GrayScale or another colorscale that closely resembles the color distribution you're interested in.
3. In the Color Mapping section,
   1. Click on the first color node.
   2. Click in the Color field and select the desired color for the lowest numeric value.
   3. Double click in the histogram to add a new node, if needed.
      1. Select the desired Color.
      2. Enter the Data Value or Position for the selected node, if needed.
   4. Adjust the Stretch and Method as desired.
   5. Click on the last color node.
   6. Click in the Color field and select the desired color for the lowest numeric value.
4. Click OK to apply the new colormap to your map.

Adding custom colormaps to the presets menu

After creating a custom colormap, you may find you want to use that colormap in many other maps.  To do this you can save the colormap as a CLR file or you can add it to the preset menu in Grapher.  To add a custom colormap to the presets menu:

1. Open the Colormap Editor and create or load your custom colormap.
2. Click Add.
3. To rename and rearrange custom presets:
   1. Click Edit to open the Edit Presets List dialog.
   2. Click and drag preset colormaps to reorganize the list.
   3. Click on a custom colormap and click Rename to open the Preset Name dialog.
   4. Enter the desired name and click OK.
   5. Click OK to close the Edit Presets List dialog.
4. Click OK to close the Colormap Editor.

Perceptually uniform colormaps for scientific data (with downloads)

Choosing the right colormap helps your data tell an honest story. For continuous scientific data like depth, elevation, or concentration, the most effective colormaps increase steadily in brightness from one end to the other, so equal steps in your data look like equal steps in color.

That steady change in brightness does more than improve accuracy. It is also what makes these colormaps readable for people with color vision deficiencies, because the information comes through even when the hues are hard to tell apart, and it means your map still makes sense when printed in grayscale.

Download any of the CLR files below and add them to your presets using the steps above. Viridis and Cividis are widely used standards in the scientific community, and the rest offer the same accuracy in a range of color themes.