Nitrosonomas and Nitrobacter Appearance?

Cleaned out my Aquaclear filter out of my 2 month old
Aquarium yesterday and noticed something strange when I rinsed out
the sponge. The crud was dark grass green as oposed to brown or black,
like in my other similar filters of my older tanks. Are there different
strains
of these bacteria? What would explain the coulour difference and wich one is
better?
....Kodiak