Organize swatches into groups based on the attribute name after a dash.

swatches-organizer.php

class Swatches_Organizer {
	private static $instances = null;

	public static function register( $taxonomy_slug ) {
		if ( self::$instances == null ) {
			self::$instances = new Swatches_Organizer( $taxonomy_slug );
		}
	}

	protected $taxonomy_slug;
	protected $current_group;
	protected $groups = [];

	protected function __construct( $taxonomy_slug ) {
		$this->taxonomy_slug = $taxonomy_slug;
		add_action( 'woocommerce_swatches_before_picker_items', [ $this, 'bind_hooks' ] );
	}

	function bind_hooks( $config ) {
		if ( $config->_attribute_name == $this->taxonomy_slug ) {
			add_action( 'woocommerce_swatches_before_picker_item', [
				$this,
				'on_woocommerce_swatches_before_picker_item'
			] );
			add_action( 'woocommerce_swatches_after_picker_item', [
				$this,
				'on_woocommerce_swatches_after_picker_item'
			] );
			add_action( 'woocommerce_swatches_after_picker_items', [
				$this,
				'on_woocommerce_swatches_after_picker_items'
			] );
		}
	}

	function unbind_hooks() {
		remove_action( 'woocommerce_swatches_before_picker_item', [
			$this,
			'on_woocommerce_swatches_before_picker_item'
		] );
		remove_action( 'woocommerce_swatches_after_picker_item', [
			$this,
			'on_woocommerce_swatches_after_picker_item'
		] );
		remove_action( 'woocommerce_swatches_after_picker_items', [
			$this,
			'on_woocommerce_swatches_after_picker_items'
		] );
	}

	function on_woocommerce_swatches_before_picker_item( $swatch_term ) {
		$this->current_group = substr( $swatch_term->term_label, strpos( $swatch_term->term_label, '-' ) + 2 );
		if ( !isset( $this->groups[ $this->current_group ] ) ) {
			$this->groups[ $this->current_group ] = [];
		}
		ob_start();
	}

	function on_woocommerce_swatches_after_picker_item( $swatch_term ) {
		$this->groups[ $this->current_group ][] = ob_get_clean();
	}

	function on_woocommerce_swatches_after_picker_items() {
		foreach ( array_keys( $this->groups ) as $group ) {
			echo '<div>';
			echo '<h4>' . $group . '</h4>';
			foreach ( $this->groups[ $group ] as $item ) {
				echo $item;
			}
			echo '</div>';
		}

		$this->unbind_hooks();
	}

}

// Register the organizer for the particular product attribute. 
Swatches_Organizer::register( 'pa_color-swatches' );