color-controls.php

<?php
/**
 * Colors controls.
 *
 * @since 1.0.0
 *
 * @param WP_Customize_Manager $wp_customize The Customizer object.
 */
function bigbox_customize_register_colors_controls( $wp_customize ) {
  $wp_customize->add_setting(
    $key, [
      'default'           => '#fff000',
      'transport'         => 'postMessage',
      'sanitize_callback' => 'sanitize_hex_color',
    ]
  );

  $wp_customize->add_control(
    new BigBox\Customize\WP_Customize_Color_Control(
      $wp_customize,
      $key,
      [
        'label'    => 'Some Color',
        'section'  => 'colors-palette',
        'palettes' => [ '#fff000', '#ff0000' ],
      ]
    )
  );
}
add_action( 'customize_register', 'bigbox_customize_register_colors_controls', 20 );