How? Working with Color
A personal approach to making maps
I’ve been working as a map designer for most of my career. Starting in black and white, then working in color for print (CMYK), to on-screen (RGB) and now online (HEX), I’ve developed a deep understanding of how color works on maps. These days, my work at Esri includes basemap design and building color ramps for ArcGIS Online.
This is one of a sequence of Story Maps where I attempt to describe some of my methods.
What used to be
My approach to color is intuitive – it always has been!
In my early days maps were created manually, compiling and drawing on to multiple sheets of material then combining them to create the final press-ready image (I discuss this in more detail here ). This process severely limited the number of colors we had available. Not in theory - we could use as many as we wanted! But the process was complex and costly, with each change in color requiring a new sheet of material. The pressure was always on to reduce the number of steps involved. That meant making some generalizations about color use.
To compound this, there was a level of guesswork in working out how that color would print – you wouldn’t really know the finished result until you ran a proof from the final negatives.
Pantone process color swatch. Versions were available for coated and uncoated paper, and gave the CMYK breakdown to achieve that color in print.
Even then, the print process could change it significantly. We would use color swatches to simulate the printed color and to give us some guidance, but it was always a bit of a lottery. Experience helped of course, and my ability to predict the look of the printed map improved over the years.
These days the result of a color choice can be seen in real time on the computer screen*, but that understanding has stayed with me.
*Different screens can give very different viewing experiences, and it’s important to remember that not everyone will see precisely the same color that you do. However, if you are aware of and expect that, it is likely that you can work around it. If you are careful about how you build your palette, the chances are that the relative color balance will remain the same.
Establishing the Color Palette for the Map
I’m going to describe my process here. I’m not advocating it– it’s what works for me!
For this exercise I’m going to work through how I developed the palette for the ‘Mid-Tone’ basemap I describe here .
Before starting, I want to make some basic decisions:
I’ve always liked the juxtaposition of blue and orange, so I started out with that. This was the starting color palette for my map...
I plan my colors out in a graphics application. I create color blocks to compare against each other, and adjust accordingly. These days. I always test my choices against a grayscale conversion and a color blindness simulator.
The grayscale version is not definitive (reds, for example, always tend to translate much darker), but it’s a useful cross-check on the relative strength of the colors.
Using a color blindness simulator is just good practice.
...but once I began working on the rest of the information, I found that the orange was too bright. I played around with it and ended up with something much more subdued.
It’s not unusual to find yourself making fundamental changes to the palette as you develop it. It's important to know when a concept is beginning to break down, and when to reset.
Frequently I’ll look back at a finished product and wonder how I got there from my original vision.
Bathymetry is available in the vector tile package. I wasn’t planning to add much content over the water, so using it was an easy decision. It’s only function here is to make the map more graphically interesting .
Generally, you want to keep things as clean and simple as possible, but you can play a bit.
There is nothing wrong with adding content for decorative purposes if it doesn’t compromise legibility or move the focus from the subject of the map.
Refining the Palette
This is the completed map:
With the concept established, I start to work out colors for the map detail.
Here, I've applied my basic palette, and worked on the reversed-out concept for countries and boundaries.
One way to approach this (although not the only way) is to look at the allocation of colors in themes. Some of them are obvious:
- It is a statement move to use anything other than blue for water.
- Parks and open space are probably going to be a variation on greens.
Here, the greens are deliberately subdued at small scales so that they fade-in.
After that it depends on the subject of the map.
So, for example, if road designations are not an important feature of the map, you may want to keep them all in variations of one color...
Here, a burgundy line/casing links all of the roads, with fills moving towards a buff/yellow. This helps to subdue the roads on the similarly colored background.
If roads are the subject of the map, you may want to use a mix of colors to define them more effectively.
This is part of a National Geographic Road Atlas simulation I used here .
Quantitative Color
For ArcGIS users (in Pro or Online), we’ve done some of the work for you by building a series of functional color ramps.
Think of a color ramp as a starting point though. If you have the time and the opportunity to take the map beyond the defaults we give you, you should consider it.
You can build a ramp directly in ArcGIS Pro (Go to ‘Symbology/Color Scheme/Format Color Scheme’, then save to a style). In ArcGIS Online you cannot build a ramp/gradient as such. However, if you use a classification, you can establish a default with one of our ramps, then adjust each color individually.
Building a Color Ramp
This is a quick guide to building your own ramp. The information is covered in more detail here .
We usually work with ten fixed points for building ramps online. Ten is a lot! It’s difficult to get a strong visual separation using one color for this many categories, but it gives us a lot of control over the final appearance of the ramp. For you, select your worst-case (up to 7 or 8 are usually OK), and build your ramp based on that.
Setting the extremes
Consider the map you are building to establish your high and low points. At the top, check on what may overlay the colors, particularly labels, and set something that will allow some contrast. If you are working with a known quantity behind your ramp (a basemap or your background information), take that into account. You don’t want the low end of the gradient to get lost in it.
Here I’ve placed the Light Gray Canvas Map behind my colors. On the left, the light color is getting lost in the background. Moving it by as little as 3% (right) is enough to open up some visual distance.
High-Low ramps
This is not as simple as building an even gradient between the top and bottom of the ramp. Differences between colors are more difficult to discern as the saturation increases, and at the dark end of the gradient the colors may be too similar.
To control this, set a mid-range stop, then set equal intervals between it and the extremes. Choose a color value for the mid-point that establishes the interval between the darker colors as greater than that between the lighter. However, aim for at least 3-5% tonal variation between each step.
Don't be afraid to make custom adjustments if you feel the ramp is not working as you intend.
Above-Below ramps
The same considerations apply, but now you are setting a mid-point that is lighter or darker, and introducing a second color. The mid-point may be a blend of your two extremes, a neutral color, or a contrasting color, depending on how you want to use the ramp.
A red-blue ramp with a blended mid-point
A red-blue ramp with a neutral mid-point
A red-blue ramp with a contrasting mid-point
Color Vision
As soon as you introduce a second color to the construction, color vision deficiency needs to be taken into account. We check this as a matter of course now for all our ramps on ArcGIS Online.
(You can find more information on working for vision deficiency here ).
What I've described here is an intuitive way of building a color palette. However, there’s nothing wrong with being scientific about color use, and plenty of work has been done by Cindy Brewer and others to help you along this path.
I’m lucky! My color choices tend to work out without me needing to analyze them too much. Not everyone can do that, and you need to find your way to a method that works for you.
This is the second of a series of 'How to' Story Maps looking at the ways I develop my work. The other sections are:
Maps and Printing (coming soon)
Andy Skinner, 2024
