I had issues getting this to work with CS5.5 while using Windows 7. This is how I fixed it.
I followed the directions found at http://doc.silverstripe.org/old/tools:dreamweaver.
I then changed C:\Program Files\Adobe\Adobe Dreamweaver CS4\configuration\Extensions.txt by adding the extension SS under HTML Documents and PHP files. Saved and closed.
After completing these two steps, the color coding was still not working. Then the did the following:
This following part is what fixed the issue for me... I had to edit the following file: C:\Users\[USERNAMEGOESHERE]\AppData\Roaming\Adobe\Dreamweaver CS5.5\en_US\Configuration\DocumentTypes\MMDocumentTypes.xml. I had to change Change Line 3 into:
<documenttype id="HTML" internaltype="HTML" winfileextension="html,htm,shtml,shtm,stm,tpl,lasso,xhtml,ss" macfileextension="html,htm,shtml,shtm,tpl,lasso,xhtml,ssi,ss" file="Default.html" writebyteordermark="false">
Save and close. Now open Dreamweaver and open a .ss file. The color coding should work.
I Hope that helps fix your problem!