Ok, I've done a little tinkering and here is a new and improved index.php for colormixing. It has dropdown lists for setting any the color value possible, and also 6 links demonstrating how you can use pre-defined colors. Hope this helps! =)
<?php
echo '<form action="backend.php" method="post">
<pre>
Red: <select name="r">';
for($num = 0; $num < 256; $num++)
{
echo '<option value="'.$num.'">'.$num.'</option>'."\r\n";
}
echo '</select>
Green:<select name="g">';
for($num = 0; $num < 256; $num++)
{
echo '<option value="'.$num.'">'.$num.'</option>'."\r\n";
}
echo '</select>
Blue: <select name="b">';
for($num = 0; $num < 256; $num++)
{
echo '<option value="'.$num.'">'.$num.'</option>'."\r\n";
}
echo '</select>
<input type="submit" value="Set color" /></form></pre>';
?>
<a href="backend.php?r=255&g=0&b=0">Red</a>
<a href="backend.php?r=0&g=255&b=0">Green</a>
<a href="backend.php?r=0&g=0&b=255">Blue</a>
<a href="backend.php?r=255&g=255&b=0">Yellow</a>
<a href="backend.php?r=255&g=0&b=255">Pinkish</a>
<a href="backend.php?r=0&g=255&b=255">Turquoise</a>