如何使R中的五大湖与海洋颜色相同？

我刚开始使用 R 制作地图。我正在尝试制作北美地图（以美国为中心），并希望五大湖的颜色与海洋的颜色相同。我当前的代码默认使它们与国家/州具有相同的颜色。关于如何改变它们的颜色有什么想法吗？也许是不同的底图？

当前代码：

library(cowplot)
library(googleway)
library(ggplot2)
library(ggrepel)
library(ggspatial)
library(sf)
library(rnaturalearth)
library(rnaturalearthdata)

world <- ne_countries(scale = "medium", returnclass = "sf")
usa <- st_as_sf(maps::map("state", fill=TRUE, plot =FALSE),
                crs = 4269)

ggplot(data = world) +
  geom_sf(color = "black", fill = "gray") +
  geom_sf(data = usa, color = "black", fill = "gray") +
  xlab("Longitude") + ylab("Latitude") +
  coord_sf(xlim = c(-123, -69), ylim = c(25, 49), expand = TRUE) +
  annotation_scale(location = "br", width_hint = 0.5, text_cex = 1) +
  annotation_north_arrow(location = "br", which_north = "true", 
                         pad_x = unit(0.15, "in"), pad_y = unit(0.3, "in"),
                         style = north_arrow_fancy_orienteering) +
  theme_bw() +
  theme(plot.title = element_text(hjust = 0.5),
        plot.subtitle = element_text(hjust = 0.5),
        text = element_text(size = 16),
        axis.text.x = element_text(size = 14, color = "black"),
        axis.text.y = element_text(size = 14, color = "black"),
        panel.grid.major = element_line(color = gray(0.5), linetype = "dashed", size = 0.5),
        panel.background = element_rect(fill = "aliceblue"))

好吧，我做了一些挖掘，结果发现自然地球具有全世界湖泊的几何形状。ne_download(type = 'lakes').

library(ggplot2)
library(ggspatial)
library(sf)
library(rnaturalearth)

科幻世界

world <- rnaturalearth::ne_countries(scale = "medium",
                                     returnclass = "sf")

北美作为 sf

n_america <- world %>% 
  filter(adm0_a3  %in% c("MEX", "CAN", "USA"))

湖泊作为SF

lakes <- rnaturalearth::ne_download(scale = 110, 
                     type = 'lakes', 
                     category = 'physical') %>% 
      sf::st_as_sf(lakes110, crs = 4269)

美国各州作为 sf

usa_states <- st_as_sf(maps::map("state", 
                                 fill=TRUE, 
                                 plot =FALSE),
                crs = 4269)

或者，美国声明为 sf （所以你不需要{maps})

devtools::install_github("ropensci/rnaturalearthhires")
usa_states <- rnaturalearth::ne_states(country = "United States of America") %>% 
 sf::st_as_sf(crs = 4269)

使用 ggplot2 绘图

ggplot() +
  geom_sf(data = n_america,
          mapping = aes(geometry = geometry),
          color = "black",
          fill = "gray")  +
  geom_sf(data = usa_states,
          mapping = aes(geometry = geom),          
          color = "black", 
          fill = "gray") +
  geom_sf(data = lakes,
          mapping = aes(geometry = geometry),
        color = "black",
        fill = "lightblue")  +
  coord_sf(ylim = c(23, 49),
           xlim = c(-123, -69),
           expand = TRUE) +
  annotation_scale(location = "br", 
                   width_hint = 0.25, 
                   text_cex = 1) +
  annotation_north_arrow(location = "br", 
                         which_north = "true", 
                         pad_x = unit(0.15, "in"),
                         pad_y = unit(0.3, "in"),
                         style = north_arrow_fancy_orienteering) +
  labs(x = "Longitude",
       y = "Latitude") +  
  theme_bw() +
  theme(axis.text.x = element_text(size = 12, color = "black"),
        axis.text.y = element_text(size = 12, color = "black"),
        panel.grid.major = element_line(color = gray(0.5), linetype = "dashed", size = 0.5),
        panel.background = element_rect(fill = "lightblue"))

随心所欲地改变海洋和湖泊的颜色。