Comparing the palette under colour vision deficiency

Roughly 8% of men and 0.5% of women have some form of colour vision deficiency (CVD). A categorical palette is only useful if its colours remain distinguishable to those viewers. This vignette shows the ten discrete poispalette colours as they appear under normal vision and under the three main types of CVD.

library(poispalette)
library(ggplot2)
library(colorspace)

The discrete palette contains ten named colours.

pois_cols()
#>      black       blue        red     yellow     purple      green light blue 
#>  "#000000"  "#3063A3"  "#E8613C"  "#F7B530"  "#821C65"  "#63BB42"  "#90BDE5" 
#>     orchid       grey    crimson 
#>  "#D888CF"  "#7D7D7D"  "#A7061E"

CVD is simulated with colorspace, which provides deutan(), protan(), and tritan() to approximate how colours appear under deuteranopia, protanopia, and tritanopia. The palette is rendered as swatches, one row per vision type.

cols <- pois_cols()

sims <- list(
  Normal = identity,
  Deuteranopia = deutan,
  Protanopia = protan,
  Tritanopia = tritan
)

swatches <- do.call(rbind, lapply(names(sims), function(vision) {
  data.frame(
    vision = vision,
    colour = names(cols),
    hex = sims[[vision]](unname(cols)),
    x = seq_along(cols),
    stringsAsFactors = FALSE
  )
}))

swatches$vision <- factor(swatches$vision, levels = names(sims))
swatches$colour <- factor(swatches$colour, levels = names(cols))

ggplot(swatches, aes(x = x, y = 1, fill = hex)) +
  geom_tile(colour = "grey40", linewidth = 0.3) +
  scale_fill_identity() +
  facet_wrap(~vision, ncol = 1, strip.position = "left") +
  scale_x_continuous(
    breaks = seq_along(cols),
    labels = names(cols),
    position = "top",
    expand = c(0, 0)
  ) +
  labs(x = NULL, y = NULL) +
  theme_minimal() +
  theme(
    axis.text.x = element_text(angle = 45, hjust = 0, vjust = 0),
    axis.text.y = element_blank(),
    panel.grid = element_blank(),
    strip.text.y.left = element_text(angle = 0),
    legend.position = "none"
  )

Under deuteranopia and protanopia the blues, green, and light blue shift toward muddy yellows and blues. Across all three deficiency types the ten colours remain distinguishable, though pairs such as blue/light blue are closer than under normal vision and are best reserved for categories that do not need to be told apart at a glance.