Add classes to programmatically added fields

Question

I have programmatically created a few content types and fields for said content types in a module I'm building, but I need to add classes to said fields.

So if I have a text field called "background_color", I would like to add a class to it called "color-picker".

Im added the instance of the field to my bundle like:

...
    'background_color' => array(
        'field_name' => $fields['field_background_color']['field_name'],
        'label' => 'The stroke color',
        'bundle' => 'nji_map',
        'entity_type' => 'node',
        'attributes' =>array('class'=>array('minicolors')),
        'widget'      => array(
            'type'    => 'text_textfield',
        ),
        'display' => array(
            'default' => array(
            'label' => 'above',
            'type' => 'text_textfield',
            ),
        ),
        'description' => 'The background color is the color between.',

    )....

Edit - Here is more of my code (node the full code snippet because there are too many fields)..

        $fields = array(
        'field_map_background_color' => array(
            'field_name' => 'field_map_background_color',
            'type' => 'text'
        ),...

$instances =  array(
    'background_color' => array(
        'field_name' => $fields['field_map_background_color']['field_name'],
        'label' => 'The background color',
        'bundle' => 'nji_map',
        'entity_type' => 'node',
        'attributes' =>array('class'=>array('minicolors')),
        'settings' => array(
            'prefix' => '<div class = "minicolors">',
            'suffix' => '</div>',
        ),
        'widget'      => array(
            'type'    => 'text_textfield',
        ),
        'display' => array(
            'default' => array(
            'label' => 'above',
            'type' => 'text_textfield',
            ),
        ),
        'description' => 'The background color is the color between.',

    ), ....

  foreach ($fields as $field) {
    field_create_field($field);
  }

  foreach ($instances as $instance) {
    field_create_instance($instance);
  }

Answer 1

Do something like this to wrap this field in a DIV class --

...
    'background_color' => array(
        'field_name' => $fields['field_background_color']['field_name'],
        'label' => 'The stroke color',
        'bundle' => 'nji_map',
        'entity_type' => 'node',
        'attributes' =>array('class'=>array('minicolors')),
        'widget'      => array(
            'type'    => 'text_textfield',
        ),
        'settings' => array(
          'prefix' => '<div class = "my_field_div_class">',
          'suffix' => '</div>',
        ),
        'display' => array(
            'default' => array(
            'label' => 'above',
            'type' => 'text_textfield',
            ),
        ),
        'description' => 'The background color is the color between.',

    )....

You would notice I have added settings along with other properties of the instance, where we can add prefix, sufix, min, max etc. I hope it works..