Using ggplot2 & geom_bar to change bar color based on 1 factor variable and bar pattern based on another factor variable

Try something like this:

library(tidyverse)
library(ggpattern)

tribble(
  ~x, ~y, ~fill, ~pattern,
  "a", 10, 1, 3,
  "a", 15, 1, 3,
  "a", 20, 1, 2,
  "b", 10, 0, 2,
  "b", 12, 0, 3,
  "b", 13, 0, 3
) |> 
  mutate(fill = factor(fill),
         pattern = factor(pattern)) |> 
  ggplot(aes(x, y, fill = fill)) +
  geom_bar_pattern(aes(pattern = pattern), stat = "identity", 
                   pattern_colour = "white")

^{Created on 2022-04-29 by the reprex package (v2.0.1)}