All 16777215 displayable colors in a webpage.
<?
$output="<table>";
for ($i=0;$i<=16777215;) {
$output.= '<tr>';
for ($j=0;$j<=255;) {
  $output.= '<td bgcolor="'.str_pad(dechex($i),6, "0", STR_PAD_LEFT).'"><font color="#FFFFFF">'.str_pad(dechex($i),6, "0", STR_PAD_LEFT).'</font> <font color="#000000">'.str_pad(dechex($i),6, "0", STR_PAD_LEFT).'</font></td>';
  $j++;
  $i++;
}
$output.= '</tr>';
}
$output.= "</table>";
file_put_contents("colors.html", $output);
?>