Actually... when i fought it, it only cast OmegaGreen and OmegaYellow, so all you have to do is cast the other elements, and let the TimeDevourer cast the green or yellow when it's that time of the sequence...
as in... (i don't remember the sequence, but if it's green red blue yellow white black...) THIS IS PROBABLY THE WRONG ORDER.
you wait for TD to cast omegagreen. then you cast a red and a blue. then you wait for the omegayellow, and then cast a white and a black.
and that's it... i don't remember if you have to cast the Chrono Cross before the sequence or after it. i think it's before.
EDIT: oh yeah, and it really wasn't that hard to beat TD to death... i mean, on my first New Game + with just Serge, it was cake. Maybe i just put too much work into custom-allocating my elements...