Palettes

Choose an appropriate color palette

A color palette is a logical selection of a group of colors. Although making this selection is not straightforward, there are some general and easy-to-follow guidelines for what looks good and what works together. Note that in these examples I’ll use a standard artist’s color wheel, where the primary color triad is red, yellow and blue. This RYB color space is an intuitive color model that you probably learned in school and was popular before display shifted the trend towards the RGB additive color space described above.

The choice of color is determined by the object being colored. Smaller objects and thinner lines need larger differences in their colors to be distinguishable from each other. In this case, you should avoid sequential color schemes (see below) that include very light colors.

When manually choosing colors, begin with a color wheel divided into discrete colors Figure fig-Color-wheel-1 a. The primary colors, Red, Yellow and Blue are arranged in an equilateral triangle. The secondary colors, Orange, Green and Violet are positioned in an inverted equilateral triangle interspersing the primary colors. Tertiary colors fill in the remaining gaps. Consider the following conventions when choosing a color scheme based on this color wheel.

Figure 1: The color wheel
Name Description Data Types Color wheel
Monochromatic Change the lightness of a single color Continuous, ordinal, date or time Figure fig-Color-wheel-1 b
Analogous Include two or more colors adjacent to each other on the color wheel Continuous, ordinal, date or time Figure fig-Color-wheel-1 c
Complementary Two colors opposite each other on the color wheel Nominal Figure fig-Color-wheel-1 d
Triadic Three colors, equally dispersed on the color wheel, forming an equilateral triangle Nominal Figure fig-Color-wheel-1 e
Split-Complementary Begin with complementary colors, but choose the two colors directly adjacent to one of them Nominal & Ordinal Figure fig-Color-wheel-1 f
Tetradic Four colors, arranged in either a square or rectangular pattern on the color wheel Nominal & Ordinal Figure fig-Color-wheel-1 g
Table 1: Color selection for continuous and categorical variables

The warm and cold color palettes are just analogous color palettes, beginning with red and excluding blue, or beginning with blue and excluding red, respectively.

Color Brewer is a simple-to-use tool for selecting well-designed color palettes to meet your specific needs.1 The color palettes are based on the HCL color space and so provide ready-to-use palettes for accurate data visualizations.

  • 1 Color Brewer can be found online at http://colorbrewer2.org/.

    • Class Description Examples
    Sequential Ranges from light (typically low values) to dark (high values) Figure fig-colorBrewer, top
    Qualitative Distinct colors to accommodate categorical data Figure fig-colorBrewer, middle
    Diverging Range from low/high contrasting colors for extreme values and light colors for mid-range values Figure fig-colorBrewer, bottom
    Table 2: Palettes are arranged into three classes

    Figure 2: Sequential, qualitative and divergent color palettes in Color Brewer.

    The Color Wheel

    Complementary Color Palettes — by hue

    Quadratic Color Palettes — by hue

    Rectangular Color Palettes — by hue

    Split-complementary Color Palettes — by hue

    Triangular Color Palettes — by hue

    Rectangular Color Palettes — by lightness

    Defining Color Palettes

    Defining color palettes.