To add predefined colors in your beaver builder’s color picker, you have to add the ff. codes to any file that get’s executed by WordPress all the time. You can create your own custom plugin. The most common file to add it is in your theme or child theme’s functions.php. Here is the code snippet:

//Add color presets for Beaver Builder color picker

function custom_color_presets( $colors ) {
    $colors = array();
      $colors[] = '#fffffff';
      $colors[] = '#000000';
      // ....
    return $colors;

add_filter( 'fl_builder_color_presets', 'custom_color_presets' );