Convert colors to imitate greyscale printing

Question

When reading this question, I started to think whether it would be possible to convert colors to imitate an average greyscale printer (assuming that your screen is calibrated)?

Answer 1

Use an HCL palette with chroma set to zero to create greyscale values that are indistinguishable to the human eye.

library(colorspace)
n <- 10
cols <- rainbow_hcl(n)
plot(seq_len(n), cex = 5, pch = 20, col = cols)

greys <- rainbow_hcl(n, c = 0)
plot(seq_len(n), cex = 5, pch = 20, col = greys)

If you want to generate the greys from your original colours, use the scales package.

library(scales)
greys2 <- col2hcl(cols, c = 0)
plot(seq_len(n), cex = 5, pch = 20, col = greys2)