Yes. I generally use the grey for white and other lighter color parts and use black on darker colors such as red, green, etc.
FYI New MGs have been announced:
March:
- MG Unicorn Coating Ver. - 8,000 Yen
April:
- MG Sword Impulse Gundam - 4,500 Yen
Source:
http://ngeekhiong.blogspot.com/2009/...l-release.html