deadsea - 8:12 pm on Apr 25, 2011 (gmt 0)

Another option is to have a single canonical url for the product. Allow the users to change the color and such through Javascript and AJAX within the page. 301 redirect the urls with the color= parameter back to the canonical. You could even support the ability for users to bookmark or email the url with a color choice in it by supporting parameters after the hash tag:

http://example.com/widget.php#color=blue

Google doesn't crawl anything after the hash tag. Your server can't do anything with information after the hash tag. The javascript on the page can see it and do the correct AJAX/Javascript on page load.