How to change the box color in the colour guide in ggplot maps?

Question

I used:

 geom_polygon(aes(color = as.factor(VALE), 
               fill = ES.PC)) + scale_color_manual(values = c("Vale do Ribeira" = 'black', "Other regions of SP" = 'white'))

to separate different regions in a ggplot2 map, but I need to change the color of the guide boxes from gray to white

those boxes with the "Vale do Ribeira" and "Other Regions" circled in red

Answer 1

One option would to use the override.aes argument of guide_legend to set the fill color of the color scale.

Adapting the default example from ?geom_polygon:

library(ggplot2)

ggplot(datapoly, aes(x = x, y = y)) +
  geom_polygon(aes(fill = value, group = id, color = factor(id2))) +
  guides(color = guide_legend(override.aes = list(fill = "white")))

DATA

ids <- factor(c("1.1", "2.1", "1.2", "2.2", "1.3", "2.3"))

values <- data.frame(
  id = ids,
  value = c(3, 3.1, 3.1, 3.2, 3.15, 3.5)
)

positions <- data.frame(
  id = rep(ids, each = 4),
  x = c(2, 1, 1.1, 2.2, 1, 0, 0.3, 1.1, 2.2, 1.1, 1.2, 2.5, 1.1, 0.3,
        0.5, 1.2, 2.5, 1.2, 1.3, 2.7, 1.2, 0.5, 0.6, 1.3),
  y = c(-0.5, 0, 1, 0.5, 0, 0.5, 1.5, 1, 0.5, 1, 2.1, 1.7, 1, 1.5,
        2.2, 2.1, 1.7, 2.1, 3.2, 2.8, 2.1, 2.2, 3.3, 3.2)
)
datapoly <- merge(values, positions, by = c("id"))

datapoly$id2 <- grepl("^1", datapoly$id)