woocommerce-custom-variation-fields-variable-php

<?php
// get the post IDs of all the product variations
$variation_ids = $product->children;

foreach( $variation_ids as $var_id ) :

    // get the data from the custom fields
    $color_hex = get_post_meta( $var_id, 'color_hex', true ); // does this product have an alternate buying option?

    // model-(attribute value)
    $model_name = 'model-'.get_post_meta($var_id, 'attribute_model', true);
    ?>

    <div class="custom_variation" id ="<?php echo $model_name; ?>">
        <div class="variations_button">
            <?php echo $color_hex ?>
        </div>
    </div><!-- #custom_variation -->

<?php endforeach; ?>