As far as I know, at this moment there is no direct way to control Philips Hue lamps using a Pebble smartwatch. A workaround is possible though, with the help of a webserver that sends the right commands to the Hue bridge as you visit a specific webpage. Here’s how I did it.

Short demonstration on Youtube

What I used:

The steps as I recall them:

apt-get install curl
curl -s https://getcomposer.org/installer | php
mv composer.phar /usr/local/bin/composer
{        
"require": { "sqmk/phue": "*" }
}

and then running

composer install
<html>
  <head>
    <title>Turn on lamp 1</title>
  </head>
  <body>
     <h1>Lamp 1</h1>

<?php

require_once 'vendor/autoload.php';

$client = new PhueClient('192.168.1.2', 'thisismyhueusername');

try {
    (new PhueCommandPing)->send($client);
} catch (PhueTransportExceptionConnectionException $e) {
    echo 'There was a problem accessing the bridge';
}

// Manually send command to get light by id
$light = $client->sendCommand(
    new PhueCommandGetLightById(1)
);
echo $light->getName(), "n";
$light->setOn(true);
// Setting brightness (0 for no light, 255 for max brightness)
$light->setBrightness(255);
// Set color temp (153 min, 500 max), changes color mode to 'ct'
$light->setColorTemp(400);

?>

  </body>
</html>

To see what you can do with Phue, check https://github.com/sqmk/Phue and the Hue developers information at http://developers.meethue.com/