def get_blue_green_from_app(app):
    """
    Returns the blue_green object if exists and it's color field if exists

    >>> get_blue_green_from_app({})
    (None, None)

    >>> get_blue_green_from_app({'blue_green': None})
    (None, None)

    >>> get_blue_green_from_app({'blue_green': {}})
    (None, None)

    >>> get_blue_green_from_app({'blue_green': {'color': None}})
    ({'color': None}, None)

    >>> get_blue_green_from_app({'blue_green': {'color': ''}})
    ({'color': ''}, '')

    >>> get_blue_green_from_app({'blue_green': {'color': 'blue'}})
    ({'color': 'blue'}, 'blue')

    >>> get_blue_green_from_app({'blue_green': {'color': 'green'}})
    ({'color': 'green'}, 'green')
    """
    if app.get('blue_green'):
        return app['blue_green'], app['blue_green'].get('color', None)
    return None, None