Here's a simple huxtable-based example (I'm the package author):
library(huxtable)
my_data <- matrix(rnorm(100), 10, 10)
my_hux <- huxtable(my_data)
# row 3, column 5, coloured border:
my_hux <- set_all_borders(my_hux, 3, 5, 1)
my_hux <- set_all_border_colors(my_hux, 3, 5, "red")
# row 7, columns 2-5, orange background:
background_color(my_hux)[7, 2:5] <- "orange"
# yellow background wherever cell value > 1
my_hux <- set_background_color(my_hux, where(my_hux > 1), "yellow")