Managed to obtain colors like so:

IEx.configure(colors: [syntax_colors: [number: :magenta, atom: :cyan, string: :green,
 boolean: :magenta, nil: :magenta]])

All this config goes in the root of your project folder in an .iex.exs file that you have to create.
Now can someone explain how to format the output of the iex shell?

Thanks

It should get formatted automaitcally.

Though this depends on your terminal width.

Edit:

You can also provide the :width config option:

https://hexdocs.pm/iex/IEx.html#configure/1-width

For me it seems to work:

iex(1)> IEx.configure(width: 30)
:ok
iex(2)> [%{id: 1, name: "Jose", username: "josevalim"}]
[
  %{
    id: 1,
    name: "Jose",
    username: "josevalim"
  }
]