Map design usually relies on colour to convey information. But what if you can’t see all the colours? You get maps in shades of grey. Colour Vison Deficiency (CVD) is more common than most people think, and it’s not just red and green. Directional maps, such as street maps for example, use colour to indicate train stations and heritage sites. Geographical maps use colour to show height of land, temperature, and to separate land from water. And it’s not just maps – websites suffer the same issues.
Many of these are age-old conventions that designers follow. So how do you know what colours are best to use? The Colblinder website give examples of what geographic maps look like to people with CVD. It also has links to other references and a colour blindness simulation tool. Although this is about maps, it can also apply to websites and printed documents, such as guidelines, and manuals where pictures and graphics are used to inform and instruct.
For research on this topic Anne Kristin Kvitle’s article is worth a read. The article is titled, “Accessible maps for the color vision deficient observers: past and present knowledge and future possibilities”.
Color is part of the visual variables in map, serving an aesthetic part and as a guide of attention. Impaired color vision affects the ability to distinguish colors, which makes the task of decoding the map colors difficult. Map reading is reported as a challenging task for these observers, especially when the size of stimuli is small. The aim of this study is to review existing methods for map design for color vision deficient users. A systematic review of research literature and case studies of map design for CVD observers has been conducted in order to give an overview of current knowledge and future research challenges. In addition, relevant research on simulations of CVD and color image enhancement for these observers from other fields of industry is included. The study identified two main approaches: pre-processing by using accessible colors and post-processing by using enhancement methods. Some of the methods may be applied for maps, but requires tailoring of test images according to map types.