Show attributes in a template (with implode function)

Hello,
I want to show attribute “color” in a template (content-product.php).
I need a way to write the comma as separator between values except for last item

Here’s the function I use:

function echo_colors(){
$colors = get_the_terms( $product->id, 'pa_color');
	if(is_array($colors)) {
		$out = "<p class='colors'>";
		foreach ( $colors as $color ) {
$out .= implode( ', ', (array)$color->name );
}
$out .= "</p>";
echo $out;
}
}

add_action('woocommerce_echo_color','echo_color'); // content-product

Then I call back the action in the content-product.php where I want the list of colors appear:

<?php do_action( 'woocommerce_echo_color' ); ?>

Here’s what I get : GREENBLUERED.
The comas don’t appear.

Please anybody could help me?
Regards;

https://wordpress.org/plugins/woocommerce/