Show R heatmap outliers in a different colour

Question

Looking to mark outliers in R matrix in a different color. Say I have the data as

1  2  4  2  5
5  4  3  2  3
1 500 5  4  2

Now I want to

Answer 1

If you want to clearly see the 500, you should specify no scaling. For example,

m <- matrix(c(1, 5, 1, 2, 4, 500, 4, 3, 5, 2, 2, 4, 5, 3, 2), 
  ncol=5)

heatmap((m<500)+0, scale="none", Rowv=NA, Colv=NA)