function twentyfifteen_customize_register( $wp_customize ) {
  $color_scheme = twentyfifteen_get_color_scheme();

  $wp_customize->get_setting( 'blogname' )->transport        = 'postMessage';
  $wp_customize->get_setting( 'blogdescription' )->transport = 'postMessage';

  if ( isset( $wp_customize->selective_refresh ) ) {
    $wp_customize->selective_refresh->add_partial(
      'blogname',
      array(
        'selector'            => '.site-title a',
        'container_inclusive' => false,
        'render_callback'     => 'twentyfifteen_customize_partial_blogname',
      )
    );
    $wp_customize->selective_refresh->add_partial(
      'blogdescription',
      array(
        'selector'            => '.site-description',
        'container_inclusive' => false,
        'render_callback'     => 'twentyfifteen_customize_partial_blogdescription',
      )
    );
  }

  // Add color scheme setting and control.
  $wp_customize->add_setting(
    'color_scheme',
    array(
      'default'           => 'default',
      'sanitize_callback' => 'twentyfifteen_sanitize_color_scheme',
      'transport'         => 'postMessage',
    )
  );

  $wp_customize->add_control(
    'color_scheme',
    array(
      'label'    => __( 'Base Color Scheme', 'twentyfifteen' ),
      'section'  => 'colors',
      'type'     => 'select',
      'choices'  => twentyfifteen_get_color_scheme_choices(),
      'priority' => 1,
    )
  );

  // Add custom header and sidebar text color setting and control.
  $wp_customize->add_setting(
    'sidebar_textcolor',
    array(
      'default'           => $color_scheme[4],
      'sanitize_callback' => 'sanitize_hex_color',
      'transport'         => 'postMessage',
    )
  );

  $wp_customize->add_control(
    new WP_Customize_Color_Control(
      $wp_customize,
      'sidebar_textcolor',
      array(
        'label'       => __( 'Header and Sidebar Text Color', 'twentyfifteen' ),
        'description' => __( 'Applied to the header on small screens and the sidebar on wide screens.', 'twentyfifteen' ),
        'section'     => 'colors',
      )
    )
  );

  // Remove the core header textcolor control, as it shares the sidebar text color.
  $wp_customize->remove_control( 'header_textcolor' );

  // Add custom header and sidebar background color setting and control.
  $wp_customize->add_setting(
    'header_background_color',
    array(
      'default'           => $color_scheme[1],
      'sanitize_callback' => 'sanitize_hex_color',
      'transport'         => 'postMessage',
    )
  );

  $wp_customize->add_control(
    new WP_Customize_Color_Control(
      $wp_customize,
      'header_background_color',
      array(
        'label'       => __( 'Header and Sidebar Background Color', 'twentyfifteen' ),
        'description' => __( 'Applied to the header on small screens and the sidebar on wide screens.', 'twentyfifteen' ),
        'section'     => 'colors',
      )
    )
  );

  // Add an additional description to the header image section.
  $wp_customize->get_section( 'header_image' )->description = __( 'Applied to the header on small screens and the sidebar on wide screens.', 'twentyfifteen' );
}