The Callout is simply a way to focus the user on a piece of text they should see.  There's different levels of callout you can use:

* `class="alert"` -- An alert style you can use to tell of impending doom. Change the variable `--red` or `--color-error` in the CSS to change it's color from the default monochrome.
* `class="success"` -- For success messages. Change `--color-good` or `--green` to change it in the CSS.
* `class="warning"` -- For warning messages. Change `--color-warning` or `--orange`.
* `class="info"` -- For info messages. Change `--color-info` or `--yellow`.

When I say "change color" I mean go into the file `static/monochrome.css` or `static/color.css` to change how it looks.