Request: scale_color_colorblind() without black

[rcragun]

Feature request

Feature request: option to not use black with scale_color_colorblind(), scale_fill_colourblind, etc.

Justification

Black is often the default color for figure content (and for content like text that surrounds figures). It seems like using black for one group, orange for another, and blue for another implies that the data in black are the default or baseline, which is often not what we want colors to communicate.

See this stackoverflow question for discussion.

Ideas for implementation

This could be a separate function: scale_color_colorblindcolors().

The option could be controlled by an argument to scale_color_colorblind() with the default set to include black: black=TRUE or noblack=FALSE.

Workaround

This is what I currently use as a workaround:

scale_color_colorblind2 = function(.color_list = 2L:8L, ...){
    scale_color_discrete(..., type = colorblind_pal()(8)[.color_list])
}

By default, this scale omits black, but you can pass a vector of color positions to .color_list to specify which colors in the colorblind palette to use.