After the final battle on Citadel with the Reapers, it was said that a red explosion was seen in many of the galaxies. Why was the explosion red? Could it have been green or blue?

by JillyPolla

Reedstilt

This is more a question for /r/AskScience, but the color of the Catalyst's radiant energy depended largely on where one was in the galaxy and one's motion relative to the propagation of the energy wave. In some areas it was red-shifted, in others it was blue-shifted. Green is right out.

primekhaos

I thought the explosion was white and gold