plot - Vary colors of axis labels in R based on another variable

Question

I usually use ggplot2, but in this case I am using the regular image() function to plot a heatmap of a large data set. I can label all the labels as red, but I want to label the y-axis with text of different colors based on a vector of color definitions that I generate:

grid = structure(c(1:12),.Dim = c(4,3))
labs = c("A","B","C")
image(1:4,1:3,grid,axes=FALSE, xlab="", ylab = "")
#This works but isn't the colors I want
axis(2,at=1:length(labs),labels=labs,las=2, adj=1,cex.axis=0.6,col.axis="red")

That generates the following image:

I would like labels A and C to be black and B to be red. This is what I tried, but it gives a "wrong length" error...

axiscolors = c("black","red","black")
axis(2,at=1:length(labs),labels=labs,las=2, adj=1, cex.axis=0.6, col.axis=axiscolors)

This is the effect I am after with some "real" data...

EDIT:

As a back-up, if this is possible in ggplot2, I might be willing to re-factor my code. There are a couple other applications I would use this for as well.

I figured out a way to plot a layer of red symbols over the top of the old labels, but would prefer a native method with the color vector, if possible...

sublabs = c("B")
axis(2,at=match(sublabs,labs),labels=sublabs,las=2, adj=1, cex.axis=0.6, col.axis="red")

Another way would be to use text() if I could put the labels outside the plot space...

text(c(1,1,1),c(1,2,3),labs,col=c("black","red","black"))

UPDATE: See below for a solution that works with ggplot2...

Answer 1

If you ignore the vectorised possibilities like text and mtext, you can get there by repeatedly calling axis. The overhead timewise will be very minimal and it will allow all the axis calculations to occur as they normally do. E.g.:

# original code
grid = structure(c(1:12),.Dim = c(4,3))
labs = c("A","B","C")
image(1:4,1:3,grid,axes=FALSE, xlab="", ylab = "")
axiscolors = c("black","red","black")

# new code    
Map(axis, side=2, at=1:3, col.axis=axiscolors, labels=labs, lwd=0, las=1)
axis(2,at=1:3,labels=FALSE)

Resulting in: