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+===== 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)