<?php
$colors = [
	'#008053',
	'#008558',
	'#009264',
	'#00A76D',
	'#00A97A',
	'#00AD7D',
	'#00B387',
	'#7FCBAE',
];
foreach($colors as $color) {
	$rgb = str_split(substr($color, 1), 2);
	$hex = hexdec($rgb[0]) * 0.2126 + hexdec($rgb[1]) * 0.7152 + hexdec($rgb[2]) * 0.0722;
	$greyscale = '#'.str_repeat(dechex($hex), 3);
	$hex = $hex / 255;
	var_dump($color.' => '.$greyscale.' => '.$hex);
}