How to color lakes and districts in GADM maps?

Question

This might be a trivial question for regular users but I still couldn't find a quick and easy answer. I'm trying to create a map of Uganda in R using data retrieved using the getData("GADM", ...)-command. Here is the map created by the code from below:

I would like to color the countries' lakes in blue and the Kabarole district in red (at the moment there are several observations marked within this district but I would prefer to color the entire district). Can somebody tell me how this can be achieved?

library(Rcpp)
library(raster)
library(ggplot2)
library(ggspatial)
library(cowplot)

uganda <- raster::getData('GADM', country='UGA', level=1) 
kampala <- data.frame(name="Kampala", long=32.5833, lat=0.31666)
fort <- data.frame(name="Fort Portal", long=30.274444, lat=0.654444)

ggplot() +
  geom_sf() +
  geom_polygon(data = uganda,
               aes(x = long, y = lat, group = group),
               colour = "grey10", fill = "cornsilk", linetype = 2) +
  geom_point(data = locations,
             aes(x = Longitude, y = Latitude),
             colour = "red",
             shape = 24,
             size = 0.5) +
  geom_point(data = kampala,
             aes(x=long, y=lat),
             colour="black",
             size=2.5) +
  geom_rect(aes(xmin = 29.8,xmax = 30.6,ymin = 0.2,ymax = 1),
            colour = "black",
            fill =  NA,
            size = 1.5,
            linetype = 1) +
  annotate(geom = "text", x = 32.5833, y = 0.5, label = "Kampala", 
           fontface = "bold", color = "black", size = 4.5) +
  annotate(geom = "text", x = 33.2, y = -0.5, label = "Lake Victoria", 
           fontface = "italic", color = "grey22", size = 4) +
  annotation_scale(data = uganda, location = "bl", width_hint = 0.5) +
  annotation_north_arrow(location = "tl",  
                         pad_x = unit(0.75, "in"), pad_y = unit(0.5, "in"),
                         style = north_arrow_fancy_orienteering) +
  coord_sf(crs = sf::st_crs(4326)) +
  theme(panel.grid.major = element_line(color = gray(.5), linetype = 'dashed', size = 0.5), 
        panel.background = element_rect(fill = 'white'),
        panel.border = element_rect(colour = "black", fill=NA)) +
  xlab("") +
  ylab("")

Cross-posted here: https://gis.stackexchange.com/posts/427691/edit