Uh, you realize at that distance its imperceptible to the human eye.
Terra isn't that close to the Rift, but I think there was a lore mention of people even on Terra who are not allowed to look into the sky and suffering from the symptoms?
I know, you are talking realworld logic.
But I fear that won't get you far here...
...even though, the "creeping" inevitable effect of the Rift's "appearance" on more and more (night) skies further and further away, and the symptoms and aftershocks it brings, (while horrific and apocalyptic astropatic messagws came long before that) would have been a cool plot-device to portray the dreadful horror of Chaos.