ggplot: How to set default color for all geoms?

Question

I\'m trying to set the default color for all geoms in a ggplot to something other than black. Note this is not about setting scale_color...

Simple example:<

Answer 1

In order to replace a geom default aesthetic with another one (for all geoms using that aesthetic), you can try the following code.

First define a function for getting default aes settings of all geoms from ggplot2

library(ggplot2)
library(purrr)

geom_aes_defaults <- function() {
  geom_names <- apropos("^Geom", ignore.case = FALSE)
  geoms <- mget(geom_names, env = asNamespace("ggplot2"))
  map(geoms, ~ .$default_aes)
}

With geom_aes_defaults() you obtain a long list of all geom aesthetic mappings

$Geom
Aesthetic mapping:


$GeomAbline
Aesthetic mapping:
* `colour`   -> "black"
* `size`     -> 0.5
* `linetype` -> 1
* `alpha`    -> NA

$GeomAnnotationMap
Aesthetic mapping:
* `colour`   -> "NA"
* `fill`     -> "grey20"
* `size`     -> 0.5
* `linetype` -> 1
* `alpha`    -> NA

$GeomArea
Aesthetic mapping:
* `colour`   -> NA
* `fill`     -> "grey20"
* `size`     -> 0.5
* `linetype` -> 1
* `alpha`    -> NA

...

The following function iterates over all geoms matching a given aesthetic and substitutes the corresponding values

replace_geom_aes_defaults <- function(name, old_aes, new_aes) {
  matching_geoms <- 
    map(geom_aes_defaults(), name) %>%
      compact() %>%
      keep(~ !is.na(.) & . == old_aes)
  geoms <- gsub("^Geom(.*)", "\\1", names(matching_geoms))
  walk(geoms, update_geom_defaults, setNames(list(new_aes), name))
}

Now you can replace colors systematically, e.g. turn black into red by

replace_geom_aes_defaults("colour", "black", "red")

or even replace fill colors (for bar plots) by

replace_geom_aes_defaults("fill", "grey35", "red")