Question: why is ulquiorra cero green?
Answer: Most Cero are a crimson color when used by Hollows, Visored or Arrancar. ... So, the color does not influence directly to the power of the Cero. In fact, the color changes depending on the user's personality and style. Ulquiorra's cero maybe stronger, but it is not related to the green color, but in Ulquiorra himself.