that wasn't a cero oscuras, it was red, cero oscuras isblack
i checked the anime because i wasn't really sure if it was or wasn't a CO seeing as how the manga is black and white
i hate to disagree with by using anime evidence but at the start (first 30 seconds) it clearly shows an average red cero being charged up in his mouth not a black cero.
Even if the manga is black and white, no cero looks like that besides Ulquiorra's Cero Oscuras.
All the anime did was change the Cero Oscuras to a regular Cero. They're allowed to change stuff and/or add stuff .