<?php
$color = array('IndianRed', 'DeepPink', 'LightSalmon', 'Orange', 'Gold', 'Violet', 'BlueViolet', 'SlateBlue', 'LimeGreen', 'DarkGreen', 'Olive', 'Teal', 'SteelBlue' , 'Blue', 'Navy', 'Maroon', 'SandyBrown', 'Chocolate', 'SaddleBrown', 'Black', 'Red', 'DarkKhaki');
$rand_color = rand(0, (count($color)-1));
echo '<span style="color: '.$color[$rand_color].'">Nội dung</span>';
?>