Paul Tol's Color Schemes
The qualitative color schemes are used as given (no interpolation): colors are picked up to the maximum number of supported values.
| Palette | Max. |
bright | 7 |
highcontrast | 3 |
vibrant | 7 |
muted | 9 |
mediumcontrast | 6 |
pale | 6 |
dark | 6 |
light | 9 |
According to Paul Tol's technical note, the bright, highcontrast,
vibrant and muted color schemes are color-blind safe. The
mediumcontrast color scheme is designed for situations needing color
pairs.
The light color scheme is reasonably distinct for both normal or
colorblind vision and is intended to fill labeled cells.
The pale and dark schemes are not very distinct in either normal or
colorblind vision and should be used as a text background or to highlight
a cell in a table.
Refer to the original document for details about the recommended uses (see references)
If more colors than defined are needed from a given scheme, the color coordinates are linearly interpolated to provide a continuous version of the scheme.
| Palette | Max. | NA value |
sunset | 11 | #FFFFFF |
nightfall | 17 | #FFFFFF |
BuRd | 9 | #FFEE99 |
PRGn | 9 | #FFEE99 |
If more colors than defined are needed from a given scheme, the color coordinates are linearly interpolated to provide a continuous version of the scheme.
| Palette | Max. | NA value |
YlOrBr | 9 | #888888 |
iridescent | 23 | #999999 |
discreterainbow | 23 | #777777 |
smoothrainbow | 34 | #666666 |
As a general rule, ordered data should not be represented using a rainbow scheme. There are three main arguments against such use (Tol 2018):
The spectral order of visible light carries no inherent magnitude message.
Some bands of almost constant hue with sharp transitions between them, can be perceived as jumps in the data.
Color-blind people have difficulty distinguishing some colors of the rainbow.
If such use cannot be avoided, Paul Tol's technical note provides two color schemes that are reasonably clear in color-blind vision. To remain color-blind safe, these two schemes must comply with the following conditions:
discreterainbowThis scheme must not be interpolated.
smoothrainbowThis scheme does not have to be used over the full range.
The maximum number of supported colors is only relevant for the qualitative color schemes (divergent and sequential schemes are linearly interpolated).
bright (7), high contrast (3), vibrant (7),
muted (9), medium contrast (6), pale (6), dark (6), light (9).
sunset (11), nightfall (17), BuRd (9),
PRGn (9).
YlOrBr (9), iridescent (23), incandescent
(11), discrete rainbow (23), smooth rainbow (34).
Tol, P. (2021). Colour Schemes. SRON. Technical Note No. SRON/EPS/TN/09-002, issue 3.2. URL: https://personal.sron.nl/~pault/data/colourschemes.pdf