Edit Prose default options

functions.php

<?php

add_filter( 'prose_settings_defaults', 'custom_prose_settings_defaults' );
/**
 * Edit default Prose design settings values.
 *
 * These values are used when options are reset, or an invalid value is submitted.
 *
 * @author Gary Jones
 * @link   http://code.garyjones.co.uk/set-prose-defaults/
 *
 * @see prose_settings_defaults() Contains the prose_settings_defaults filter hook.
 *
 * @param array $defaults Array of default values with the key as the mapping name.
 *
 * @return array Amended array.
 */
function custom_prose_settings_defaults( $defaults ) {

    $defaults['body_font_color']       = '#FFE09E';
    $defaults['body_font_family']      = "'Arial Black', Gadget, sans-serif";
    $defaults['body_font_color']       = '#111111';
    $defaults['body_font_size']        = '14';
    $defaults['body_background_color'] = '#ED43F1';

    return $defaults;

}