Colors in R

This tutorial covers the specification of colors for graphics in R.

Color Specification

Named Colors

When using simple colors, using the predefined color names will usually be adequate and will keep your code readable.

A complete list of available names is below.

barplot(runif(5), col="navy", fg="white", las=1, xaxs='i', yaxs='i', ylim=c(0,1))

abline(a=0, b=0, lwd=3, col="black")

Hex Codes

When you want to be more specific with your color definitions, you can use RGB hex codes in the same manner as those used in HTML and CSS.

Six-digit codes are in the format #RRGGBB where each color is specified in a two-digit hexadecimal value from 00 to FF.

plot(runif(10), col="#C00000", type="l", lwd=3, fg="white", las=1, xaxs='i', yaxs='i', ylim=c(0,3))

lines(runif(10) + 1, col="#008000", lwd=3)

lines(runif(10) + 2, col="#000080", lwd=3)

abline(a=0, b=0, lwd=3, col="#000000")

Hex Codes with Transparency

Eight-digit codes are in the format #RRGGBBAA, with the last two digits specifying alpha (transparency) where 00 is completely transparent (invisible) and FF is completely opaque.

plot(runif(10), col="#C00000", type="l", lwd=3, fg="white", las=1, xaxs='i', yaxs='i', ylim=c(0,3))

lines(runif(10) + 1, col="#008000", lwd=3)

lines(runif(10) + 2, col="#000080", lwd=3)

grid(nx=NA, ny=NULL, lty=1, col="#00000040")

abline(a=0, b=0, lwd=3, col="#000000")

Tuples

Colors can be specified as RGB, RGBA, HSV, and HSVA tuples, although using this format can be cumbersome unless you need to manipulate colors programattically.

Color levels are specified in the range of 0 to 1, unless the maxColorValue parameter is set differently.

The rgb() and hsv() functions can be used to convert tuples to hex codes.

plot(runif(10), col=rgb(0.7, 0, 0), type="l", lwd=3, fg="white", las=1, xaxs='i', yaxs='i', ylim=c(0,3))

lines(runif(10) + 1, col=rgb(0, 0.5, 0), lwd=3)

lines(runif(10) + 2, col=hsv(2/3, 1, 0.5), lwd=3)

grid(nx=NA, ny=NULL, lty=1, col=hsv(0, 0, 0, 0.25))

abline(a=0, b=0, lwd=3, col=hsv(0, 0, 0))

Palettes

Color Ramps

Color ramps are palettes of colors interpolated between a fixed set of colors.

The colorRampPalette() takes a vector of colors and returns a function that is passed the number of desired colors

barplot(runif(5), col=colorRampPalette(c("green4", "gray", "navy"))(5), 
	fg="white", las=1, xaxs='i', yaxs='i', ylim=c(0,1))

grid(nx=NA, ny=NULL, lty=1, col="#00000040")

abline(a=0, b=0, lwd=3, col="black")

Color ramps are particularly useful for choropleth maps. The colorRampPalette() function can be passed directly as the pal parameter.

library(sf)

states = st_read("2015-2019-acs-states.geojson")

states = st_transform(states, 3082)

plot(states["Median.Household.Income"], breaks="quantile", 
	pal=colorRampPalette(c("red", "lightgray", "navy")))

Predefined Color Ramps

R comes with a set of predefined color ramp functions.

rainbow()

barplot(runif(5), col=rainbow(5), fg="white", 
	las=1, xaxs='i', yaxs='i', ylim=c(0,1))

grid(nx=NA, ny=NULL, lty=1, col="#00000040")

abline(a=0, b=0, lwd=3, col="black")

heat.colors

library(sf)

states = st_read("2015-2019-acs-states.geojson")

states = st_transform(states, 3082)

plot(states["Median.Household.Income"], breaks="quantile", pal=heat.colors)

terrain.colors

library(sf)

states = st_read("2015-2019-acs-states.geojson")

states = st_transform(states, 3082)

plot(states["Latitude"], breaks="quantile", pal=terrain.colors)

topo.colors

library(sf)

states = st_read("2015-2019-acs-states.geojson")

states = st_transform(states, 3082)

plot(states["Median.Age"], breaks="quantile", pal=topo.colors)

cm.colors

library(sf)

states = st_read("2015-2019-acs-states.geojson")

states = st_transform(states, 3082)

plot(states["Percent.Foreign.Born"], breaks="quantile", pal=cm.colors)

Color Names List

The following are available color names in R as listed from the colors() function. Code for creating this listing is here...

Grays (R == G == B)

Reds (R > G & R > B)

Blues (B > R & B > G)

Greens (G > R & G > B)

Yellows (R == G & R > B)

Cyans (G == B & G > R)

Magentas (R == B & R > G)