Sort WooCommerce Product Attribute Values on single product page only for specific attributes. Details on: https://abdulawal.com/?p=1463

woocommerce-sort-attribute-values-for-specific-attribute.php

/**
 * Sort Attribute values in ascending order for specific attributes
 * @param  array $args 
 * @return array return sorted $args array
 */
function abd_sort_wc_attribute_values( $args ){
  if( $args['attribute'] == "Attribute Name" ){ // replace Attribute Name with your attribute's name
    $get_options 		  = $args['options'];
    asort( $get_options );
    $args['options'] 	= $get_options;
    return $args;
  }
}

add_filter( 'woocommerce_dropdown_variation_attribute_options_args', 'abd_sort_wc_attribute_values', 10, 1 );