Build unique colours for objects automatically

gistfile1.txt

$background_color = substr(md5($unique_id),0,6);

$r = hexdec(substr($background_color,0,2));
$g = hexdec(substr($background_color,2,2));
$b = hexdec(substr($background_color,4,2));
$l = ($r*0.2126)+($g*0.7152)+($b*0.0722);

$text_color = ($l >= 128)? '000000' : 'ffffff';