Question: If I have a histogram:

```
> hist(faithful$waiting,seq(min(faithful$waiting),max(faithful$waiting)))

```

and a list of "special" frequencies:

```
> c(51, 52, 57, 59, 64)

```

is it possible to colour the bars corresponding to these special frequencies a different colour from the rest of the histobram?

Answer: 
You could simply create a vector of the colors and use the `col` option.

```
data(faithful)

# make sure frequencies in order and unique for the histogram call
special <- ifelse(sort(unique(faithful$waiting)) %in% c(51, 52, 57, 59, 64), "red", "white")

# same call with the 'col' option
hist(faithful$waiting,seq(min(faithful$waiting),max(faithful$waiting)), col=special)

```

![enter image description here](https://i.stack.imgur.com/6tVJF.png)
Fun with ggplot2...

```
faithful$special <- faithful$waiting %in% c(51, 52, 57, 59, 64)

library(ggplot2)

ggplot(data = faithful, aes(x = waiting, fill = special)) +
  geom_histogram(binwidth = 1, colour = 'white')

```

![enter image description here](https://i.stack.imgur.com/Ju7EB.png)