Overlay Bar Plot

I am trying to turn the first overlay bar plot into the second which allows for comparison of 2 variables instead of just one. Included my current code below which creates the first chart comparing one variable to its mean. Thanks in advance for taking a look!

  output\$p1 <- renderPlot({

ggplot(rating()) +
geom_col(aes(x = factor(RATING,levels =c('Cash','AAA','AA+','AA','AA-')),
y = pct_rating),
fill = "blue", width = 0.2) +
geom_col(aes(x = RATING, y = mean_pct_rating),
alpha = 0.3, fill = "red", width = 0.6) +
labs(title = "Rating Distribution", x = "Rating", y = "Percent") +
theme(plot.title = element_text(hjust = 0.5),
axis.text.x = element_text(size = 8,angle = 45)) +
scale_y_continuous(labels = scales::percent_format(accuracy = 1))})