function change_image_varition_source( $src, $value_slug, $tax_slug ) {
$product = new WC_Product_Variable( get_the_ID() );
$variations = $product->get_available_variations();

foreach ( $variations as $variation ) {

  $src = $variation['image']['thumb_src'];
}

return $src ;
}
add_filter( 'woocommerce_swatches_get_swatch_image', 'change_image_varition_source', 10, 3 );