Color picker HSL mode

I'm trying to output a single color to use in a CSS variable, but am unable to output the color value in HSL. I can get it to output HEX and RGBa, but not HSL.

In the field group I have the color picker option "mode" set to "hsl".

Here's the function I'm calling in functions.php within WP:

function my_header_hook() {
	$post_color = rwmb_meta(post_color_theme);
	if ($post_color) {
		echo '<style type="text/css">
				:root{
				--post-color:'.$post_color.';
			</style>';
	}
}
add_action( 'wp_head', 'my_header_hook' );