Say it really was an alien spacecraft, then the color changes could be blue- and redshift as your technology lets you seemingly alter the order of events of an

Say it really was an alien spacecraft, then the color changes could be blue- and redshift as your technology lets you seemingly alter the order of events of an acceleration and a deceleration at a far away destination. Giving a solution to GR that would create this effect is much beyond me but I would love to investigate the implications of such a universe.