Are the red cubes required to complete the game?

[PewienCzlowiek]

I already have all the normal and anti cubes and I have seen 2 endings. Is there a third one, that requires the red cubes?

[RHICTKY]

There is no ending unlocked with the red cubes. They do add to the completion percent, though. You'll need all 3 if you want the maximum 209.4%