<?php
if ( isset($_GET['color'])){
   preg_match("/([0-f]{2})([0-f]{2})([0-f]{2})/", $_GET['color'], $regs);
   $r=HexDec($regs[1]);
   $g=HexDec($regs[2]);
   $b=HexDec($regs[3]);
   header ('Content-type: image/gif');
   echo pack("c*",0x47,0x49,0x46,0x38,0x39,0x61,0x01,0x00,0x01,0x00,0x91,0xFF,0x00,0xFF,0xFF,0xFF
                 ,$r,$g,$b,0x00,0x00,0x00,0x00,0x00,0x00,0x21,0xF9,0x04,0x01,0x00,0x00,0x00
                 ,0x00,0x2C,0x00,0x00,0x00,0x00,0x01,0x00,0x01,0x00,0x40,0x02,0x02,0x4C,0x01,0x00
                 ,0x3B);
}
?>