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Color palettes to convey information to color-impaired viewers and on different output devices


Which of Ferret's color palettes best convey information to color-impaired viewers?

What palettes will show up well if I photocopy the output, or display it using LCD projectors, Laptop and CRT screens, and color printers?


The article "The End of the Rainbow? Color Schemes for Improved Data Graphics", by A. Light and P. J. Bartlein, (2004) EOS 85(40), p. 385, 391 discusses shortcomings of some of the common color schemes used in scientific publication. It explores types of color palettes which better distinguish the desired features of the data. This article is available on-line at

Articles and notes on this topic from EOS are available at Look at the last few pages for a response to the original article "Forum: Comment on Color Schemes for Improved Data Graphics" and the reply to this comment. These make a helpful discussionof the issues involved and useful color palettes for different sorts of data.

The article references two web sites where one can view these palettes and access their definitions. The sites are the ColorBrewer tool at and from the University of Oregon Data Graphics Research group, Department of Geography,


We have implemented as Ferret palette files some of the color schemes discussed in the EOS article and the two web sites it references. Their palette names, some of their properties, and a simple example of each are in the tables below.

Recall that in Ferret you can change to a new palette using the /PALETTE= qualifier on a SHADE or FILL command:

   yes? SHADE/I=1:10/J=1:10/PAL=green_magenta i-j
   yes? FILL/I=1:100/J=1:100/PAL=blue_darkred cos(i/8) + sin(j/6)
or, you can change to a particular palette for all subsequent plots with the PALETTE command:
   yes? PALETTE blue_green_yellow
   yes? USE etopo20
   yes? SHADE rose
   yes? FILL/x=12w:35e/y=25:60 rose   ! this plot also done with blue_green_yellow

   yes? USE levitus_climatology
   yes? PALETTE red_purple   ! change to red_purple palette for next plots...
   yes? FILL/K=1 salt

The ColorBrewer tool allows us to view different palettes as color bars and in a sample map. It lists properties and advantages of each one. The types we've implemented for Ferret are sequential and diverging. Here we list whether the color schemes are distinguishable by color-impaired viewers and whether they will withstand black-and-white photocopying. The ColorBrewer site also evaluates how well the color schemes show up on various output devices, such as LCD projectors, Laptop and CRT screens, and color printers.

Most of the palettes here are listed in pairs, e.g. blue_green_yellow and yellow_green_blue. These pairs contain the same colors, in reverse order. The purple_red and red_purple palettes contain different sets of colors; purple_red having dark red to light purple and red_purple having dark purple to light red.
Name Type Color-
sequential Y Y blue_green_yellow figure

example script
diverging Y N green_brown figure

example script
diverging Y N orange_purple figure

example script
sequential Y ? yellow_orange_brown figure

example script
sequential Y Y orange_red figure

example script
purple_red sequential Y ? purple_red figure

example script
red_purple sequential Y ? red_purple figure

example script

At the University of Oregon site, a number of palettes are defined and discussed. Here is a list of several that we have implemented for Ferret, with comments from the University of Oregon Data Graphics Research group. For all of these palettes except the last, categorical_12_step, there are pairs of palettes which contain the same colors in reverse order.

Useful for temperature-like data, with a subjective interpretation (blue=cold, red=hot) blue_darkred figure

example script
Useful for data with a dry (brown) vs. wet (blue) association blue_brown figure

example script
Useful for data without a specific subjective color association blue_darkorange figure

example script
Useful for data with a winter (blue) vs. summer (green) association blue_green figure

example script
Bright blue to Bright orange colors. Useful for data like sea-level pressure, with a subjective association (blue=low, wet, orange=high, dry) blue_orange figure

example script
Useful for generic diverging data. Colors can be differentiated by color-deficient viewers green_magenta figure

example script
categorical_12_step Attempt at a categorical color scale with colors that may be distinguishable to all viewers categorical_12_step figure

example script

Last modified: 3-Jan-2005