Zeileis, Achim and Hornik, Kurt
Choosing Color Palettes for Statistical Graphics.
Research Report Series / Department of Statistics and Mathematics, 41.
Department of Statistics and Mathematics, WU Vienna University of Economics and Business, Vienna.
Statistical graphics are often augmented by the use of color coding information contained in some variable. When this involves the shading of areas (and not only points or lines) - e.g., as in bar plots, pie charts, mosaic displays or heatmaps - it is important that the colors are perceptually based and do not introduce optical illusions or systematic bias. Here, we discuss how the perceptually-based Hue-Chroma-Luminance (HCL) color space can be used for deriving suitable color palettes for coding categorical data (qualitative palettes) and numerical variables (sequential and diverging palettes). (author's abstract)