I just did a Hefe and it definitely didn't go as planned. I too had lower numbers than I anticipated with my efficiency right around 60%. Mine was also greenish grey when I put it in the primary. It's now a nice yellow-ish color. I also put in a blowoff tube, as many suggest doing with hefe's and it worked like a charm I didn't lose any beer...just a whole lot of bubbling. It's still going a week later.
On Tap: Hobgoblin, Coffee Stout
Bottled: Arrogant Bastard clone, Summit IPA, Apfelwein