I too have noticed the black and dark green pollen coming in lately.  A
member of my Beekeepers Association identified the black pollen as
"Joe Pye Weed" (sorry no Latin).  Joe Pye Weed is a moisture loving
plant and blooms in areas not yet taken over by Purple Loosestrife (again
no Latin).  I have no guess about the dark green stuff.  I was amazed at
the amount of the dark green and black pollen the bees have been bringing
in - it was definitely the largest load harvested from my Stauffer pollen
trap this season.  I try to empty the trap daily when it's activated.  I
trap only enough pollen from a single trap to have sufficient quantity
to mix with pollen substitutes for early spring patties.
 
Aaron Morris - I think, therefore I bee!