By default, the hist() function automatically determines the number of bars to display, based on the data. The breaks argument controls this.
You can also use a palette of colors instead of a single color, by using the following command:
> hist(mpg, col = rainbow(12))
The following diagram is the colored histogram:
The rainbow() function returns a color palette with the color spectrum broken into the number of distinct colors specified, and the hist() function uses one color for each bar.