customize ggplot2 axis labels with different colors

Question

I have a basic bar graph I\'ve created from ggplot2. The y variable contains both positive and negative values and about half the vector of values are negative. I would like

Answer 1

You can provide a vector of colors to the axis.text.x option of theme():

a <- ifelse(data$category == 0, "red", "blue")

ggplot(data, aes(x = x, y = y)) + 
    geom_bar(stat = "identity", aes(fill = category)) +
    theme(axis.text.x = element_text(angle = 45, hjust = 1, colour = a))