Color coding for data visualization

Visualization is a process of mapping data onto visual dimensions to create a pictorial representation. A successful visualization provides a representation which allows the user to gain insight into the structure of the data or to communicate aspects of this structure effectively, The use of color for encoding information can greatly improve the observer’s understanding of the information depicted by image and his/her capacity for remembering it. However, many aspects of color itself and of its use are unknown to both users and system designers. Users are often allowed to choose colors that can not be reproduced, that can not be distinguished by the human eye, or are easily misinterpreted. The broad range of variables involved, as well as the interactions and the trade-offs among them, pose difficult problems in selecting specific colors, in predicting their appearance when they are seen in relation with others, and in predicting the observers’ interpretation and reaction to them. These problems can not be solved without a working knowledge about color reference systems, color reproduction technologies, mechanism of color perception, users’ cultural and emotional reactions. The goal of this paper is to critically discuss how a color scale should be designed to effectively represent both qualitative and quantitative information. Color coding requirements, with regard to the task at hand, the characteristics of the media, and the characteristics of data to be coded are therefore analyzed providing examples and references to related works.