## Arrow colors

You can change the colors of the arrows and messages as followings:

```
a -[#red]> b : <color blue> some message</color>
```

## Collections

There is a "collections" participant type:

```
collections "Things" as things
```

## Hidden returns

There is sometimes some weirdness when returning after a self call when there is no explicit return.  You can add a hidden return to fix this using:

```
a -> b++ : do stuff
b -> b : do stuff to self
b -[hidden]-> a : hidden return to fix weirdness
```