How to customize background colors based on (characters, NA) contents in multiple columns using gt

Question

Based on the code and data from this link, we can set background colors for the cells of multiple columns based on string contents using gt package:

library(gt)
library(tidyverse)

id <- c(1,2,3,4,5)
res1 <- c("true", "true", "false", "true", "false")
res2 <- c("false", NA, NA, "true", "true")
res3 <- c("true", NA, NA, "true", "true")
df <- data.frame(id, res1, res2, res3)

df %>% 
  gt() %>% 
  data_color(
    columns = c("res1", "res2", 'res3'),
    colors = c("green", "red", 'gray'),
    apply_to = "fill",
    autocolor_text = FALSE)

But as you may noticed, for res3, the color for true is green instead of red as in other two columns. If I hope to set red for true, green for false and gray for NA, for these 3 columns, if in case, they have other values such as yes, no, etc., just keep as original.

How could we solve this problem? Many thanks at advance.

Update1: an alternative solution with tab_style(), but not concise:

df %>% 
  gt() %>% 
  tab_style(
    style = list(
      cell_fill(color = 'red')
    ),
    locations = cells_body(
      columns = res1,
      rows = res1 == "true"
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'red')
    ),
    locations = cells_body(
      columns = res2,
      rows = res2 == "true"
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'red')
    ),
    locations = cells_body(
      columns = res3,
      rows = res3 == "true"
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'green')
    ),
    locations = cells_body(
      columns = res1,
      rows = res1 == "false"
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'green')
    ),
    locations = cells_body(
      columns = res2,
      rows = res2 == "false"
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'green')
    ),
    locations = cells_body(
      columns = res3,
      rows = res3 == "false"
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'gray')
    ),
    locations = cells_body(
      columns = res1,
      rows = res1 == NA
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'gray')
    ),
    locations = cells_body(
      columns = res2,
      rows = res2 == NA
    )
  ) %>% 
  tab_style(
    style = list(
      cell_fill(color = 'gray')
    ),
    locations = cells_body(
      columns = res3,
      rows = res3 == NA
    )
  )

Update2: How to correctly set gray color for NA cells?

cols <- c('res1', 'res2', 'res3')
df %>% 
  # mutate_each_(funs(factor(.)), cols)
  mutate_at(cols, factor) %>% 
  gt() %>% 
  data_color(
    columns = cols,
    colors = scales::col_factor(
      palette = c('green', 'red', 'gray'),
      domain = c('false', 'true', NA)
    ),
    apply_to = "fill",
    autocolor_text = FALSE
  )

Update3: I set palette = c("green", "red", 'yellow'), domain = c("false", "true", '-'), why it's not shown green for false, red for true, and yellow for -?

id <- c(1, 2, 3, 4, 5)
res1 <- c("true", "true", "false", "true", "false")
res2 <- c("false", NA, NA, "true", "-")
res3 <- c("true", NA, NA, "true", "true")
df <- data.frame(id, res1, res2, res3)

df %>% 
  mutate_at(cols, factor) %>% 
  gt() %>% 
  data_color(
    columns = cols,
    colors = scales::col_factor(
      palette = c("green", "red", 'yellow'),
      domain = c("false", "true", '-'),
      na.color = 'gray'
    ),
    apply_to = "fill",
    autocolor_text = FALSE
  )

References:

Set background color if one cell's (of multiple columns) content is specific string using gt package

Answer 1

With regard to Update 2, the version with character strings, this should work:

df %>% 
  mutate_at(cols, factor) %>% 
  gt() %>% 
  data_color(
    columns = cols,
    colors = scales::col_factor(
      palette = c("green", "red"),
      domain = c("false", "true")
    ),
    apply_to = "fill",
    autocolor_text = FALSE
  )