HDA-branded continuous color scale — scale_color_hda

A sequential or diverging colorspace HCL ramp, tuned and CVD-checked against protanopia, deuteranopia, and tritanopia in the Ramp Lab review (plans/ramp-lab/REVIEW.md).

Usage

scale_color_hda_c(
  palette = c("sequential", "diverging"),
  direction = 1,
  na.value = .brands$hda$na_color,
  guide = "colorbar",
  ...
)

scale_colour_hda_c(
  palette = c("sequential", "diverging"),
  direction = 1,
  na.value = .brands$hda$na_color,
  guide = "colorbar",
  ...
)

Arguments

palette: One of "sequential" (default) or "diverging"
direction: For palette = "sequential", 1 (default) maps higher values to darker colors; -1 reverses so higher values are lighter. For palette = "diverging", 1 (default) maps low values toward the first arm and high values toward the second, as constructed in the Ramp Lab review; -1 swaps which arm represents low vs. high.
na.value: Default color for NA values (#cfcfd0, HDA Light Gray)
guide: Legend representation for scale
...: Other arguments passed on to ggplot2::continuous_scale()

Value

A ggplot2::continuous_scale() object.

Diverging palette usage

7-class diverging maps built from these ramps lose sign distinction in their innermost class pair under protanopia (structural to the shared cream center) — always pair a palette = "diverging" map with a legend or direct labels. See plans/DECISIONS.md (2026-07-18).

HDA diverging is provisional

HDA's diverging ramp (Blue vs Coral) is pending a follow-up Ramp Lab pass before final adoption (see plans/DECISIONS.md, 2026-07-18). PHA's 2026 rebrand moved its diverging arms to Blue vs Orange, which widened the cool-arm gap between the two brands from 16 to 32 degrees, but the HDA pass is still open on its own terms. It ships now so the scale matrix is complete; treat it as subject to change.

Examples

library(ggplot2)
ggplot(mtcars, aes(wt, mpg, color = disp)) +
  geom_point() +
  scale_color_hda_c()