===== Safe Colours in the Web =====

==== The colour scheme ====

<php>
  echo '</p><table summary="safe colours in the Web">' . "\n";
  for ($R = 0x0; $R <= 0xf; $R += 0x3) {
    $ROT = sprintf("%x", $R);
    $tf = ($R == 0xf) ? "#000" : "#fff";
    for ($G = 0x0; $G <= 0xf; $G += 0x3) {
      echo "<tr>\n";
      $GRUEN = sprintf("%x", $G);
      if ($G >= 0xc) { 
        $tf = "#000"; 
      }
      for ($B = 0x0; $B <= 0xf; $B +=0x3) {
        $BLAU = sprintf("%x", $B);
        echo '      <td style="background-color:#' . "$ROT$GRUEN$BLAU" . '; color:' . "$tf" . ';" width="100" align="center">';
        echo "# $ROT $GRUEN $BLAU</td>\n";
      } // for $B
      echo "    </tr>\n";
    } // for $G
  } // for $R
  echo "</table>\n<p>";
</php>

Colour numbers are given in XHTML style; for HTML style, you may "double" the values, so ''#c3f'' becomes ''#cc33ff''.

==== and the source code: ====
<code php>
echo '<table summary="safe colours in the Web">' . "\n";
for ($R = 0x0; $R <= 0xf; $R += 0x3) {
  $ROT = sprintf("%x", $R);
  $tf = ($R == 0xf) ? "#000" : "#fff";
  for ($G = 0x0; $G <= 0xf; $G += 0x3) {
    echo "<tr>\n";
    $GRUEN = sprintf("%x", $G);
    if ($G >= 0xc) { $tf = "#000"; }
    for ($B = 0x0; $B <= 0xf; $B +=0x3) {
      $BLAU = sprintf("%x", $B);
      echo '      <td style="background-color:#' . "$ROT$GRUEN$BLAU" . 
           '; color:' . "$tf" . ';" width="100" align="center">';
      echo "# $ROT $GRUEN $BLAU</td>\n";
    } // for $B
    echo "    </tr>\n";
  } // for $G
} // for $R
echo "</table>\n";
</code>

Of course the "central" ''echo'' invocation can be written another way:
<code php>
      echo '      <td style="background-color:#',
           $ROT, $GRUEN, $BLAU, '; color:', $tf, 
           ';" width="100" align="center">';
</code>

If you want to change the output so that HTML values are displayed, you have to make following modifications:
  * the condition for the loop reads ''%%<%%= 0xff''
  * the loop counter is incremented with ''+= %%0x33%%''
  * the output changes to ''%02x'' (results in 00 bis ff) or ''%02X'' (results in 00 bis FF)