There are quite a few posts describing how you can get Dreamweaver to open unrecognised files with the same colour-coding as used on a recognised file type. For instance Dreamweaver doesn't know that a .module file should use the same colour-coding as a standard .php file, or that .sass & .scss files should be treated as .css files.
For example, the below details how you add the .module format to be recognised as a PHP file type in Dreamweavers MMDocumentTypes.xml file.
<documenttype id="PHP_MySQL" servermodel="PHP MySQL" internaltype="Dynamic" winfileextension="php,php3,php4,php5,module" macfileextension="php,php3,php4,php5,module" file="Default.php" writebyteordermark="false">
What tripped me up when trying to get colour-coding working by setting the files document type, is the location of the configuration files in Dreamweaver 5.5 and above. Most tutorials tell you to change the MMDocumentTypes.xml and Extensions.txt files that are located at:
/Applications/Adobe Dreamweaver CS5.5/Configuration/DocumentTypes/MMDocumentTypes.xml
/Applications/Adobe Dreamweaver CS5.5/Configuration/Extensions.txt
C:\Program Files (x86)\Adobe\Adobe Dreamweaver CS5.5\configuration\DocumentTypes\MMDocumentTypes.xml
C:\Program Files (x86)\Adobe\Adobe Dreamweaver CS5.5\configuration\Extensions.txt
What I found though is that the updates weren't taking effect, due to the fact that the actual files that needed to be edited are located under the specific users application config folders.
~/Library/Application Support/Adobe/Dreamweaver CS5.5/en_US/Configuration/DocumentTypes/MMDocumentTypes.xml
~/Library/Application Support/Adobe/Dreamweaver CS5.5/en_US/Configuration/Extensions.txt