add-color-attribute.php

<?php

/**
 * Add color attribute.
 * 
 * The attribute "Color" with a slug of "color" must already exist here: 
 * WordPress Admin Area > Products > Attributes.
 */
add_filter( 'dfrpswc_filter_attribute_value', 'mycode_add_color_attribute', 20, 6 );
function mycode_add_color_attribute( $value, $attribute, $post, $product, $set, $action ) {
	if ( $attribute == 'pa_color') {
		if ( isset( $product['color'] ) )  {
			$value = $product['color'];
		}
	}
	return $value;
}