Just to add my reading to the mix because I only talked about this in the issue review threads. The idea of blue and red shift universes suggests relative movement. Hickman took great pains to highlight the two colours of incursions and Molecule Man referenced them on the page immediatley preceeding the image of the first red incursion.
So by my thinking: Molecule Man is a fixed point that anchors the multiversal timelines together. As long as there is a Molecule Man time remains stable across the Multiverse. If you kill a Molecule Man his remnant world is blue shifted. - Blue shifting implies motion towards the observer and most incursions are red shited which implies motion away from the observer.
By my way of thinking the multiverse is expanding in a simmilar way to the universe, and blue shift incursions represent a collapsing timeline.
Putting these two ideas together I think the blue shift worlds are contracting very slightly in their timeline after they have become uncoupled from the mutiverse. Once billions of these blue realities exist there is stress in the multiverse with the contracting timelines causing incursions. This in turn causes universes to totally collapse and has a further contracting effect on the timelines. This secondary contraction was what Reed noticed early on and is part of his diagram. He had no way of knowing at that stage that there was a primary reason for the contractions so he put it down to a single universe collapsing for unknown reasons.