Please ignore Sergey's answer he was trying to be smart and failed.
Yes you can control the keyword recognition and colourization which is held in a user data file called Usertype.dat which you will find in "C:\Program Files\Microsoft Visual Studio 11.0\Common7\IDE" for 32 bit versions of windows or "C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE" for 64 bit versions of windows.
You can open and edit the file with any simple text editor like notepad or wordpad.
Kip Irvine has for example done a full blog on how to modify VS 2012 to deal with ASM files in VS 2012 which you might find helpful
That includes setting up call the external program directly from within VS 2012 which might also interest you.