A couple of weeks ago we spent some time exploring data visualization best practices – e.g., some of the basic principles of human visual perception, when to use different chart types, use of colour and highlight, etc. A good visualization can help us identify patterns, trends, exceptions, and outliers that might be difficult or impossible to see in the raw data.
In today’s blog, I wanted to mention some of the things we noted about the use of colour specifically. This is certainly not meant to be an exhaustive discussion of colour theory – just a few tips & tricks to keep in mind when designing visualizations.
How do the colours look on the screen or device on which people will be viewing them? Lighter colours can appear washed out on a projector screen, for instance.
Can you see the text easily against the background? Yellow text on a white background can be hard on the eyes; same with blue text on a black ground.
If using multiple colours, are they distinct enough from each other to allow us to easily differentiate among them?
Don’t forget that colourblind people will struggle with a red / green colour palette. Choose an alternative palette (blue / orange is a favourite) to ensure that everyone will be able to read your charts properly.
3. Connotations & Context
Consider the psychological associations of individual colours and the kinds of responses they can provoke in different contexts.
Red and blue are often associated with political parties in the United States, for example. Green is often associated with growth or positive numbers in a business context, while red is often associated with losses or negative numbers (but don’t forget about the aforementioned red / green accessibility issue!). If your viz is on a certain sports team or brand, you could use their official colours as your palette.
It can also be important to consider the cultural implications of certain colours. For example:
In many Western cultures, the colour red can be associated with love, passion, anger, or danger. In China, it is associated with good luck and marriage (brides often wear it on their wedding day).
Purple is strongly associated with royalty in many Western cultures, and with mourning in some South American cultures.
Green often has religious connotations in Arab cultures, but is also associated with death in some South American cultures, with life in some African cultures, and with success or envy in some Western cultures.
Finally, also consider staying away from stereotypical colour associations – e.g., blue for males and pink for females.
4. Judicious use of colour
Another tip from Carl & Andy was to build an entire viz in greyscale, and then throw on colour only where you need it to make a point – e.g. as a highlight.