Of course, If you are going to explore the maybe-Watchmen origins if the pre-52 Superman, then clearly referencing Alan Moore's run on Swamp Thing is the way to do it.
This was seen as a sign of Dr Manhattan. Was he here? Was he actually this Superman, transformed by Dr Ozymandias, posing as Mr Oz?
Superman Annual, for the first time, joins the blue handprint and the presence of Dr Oz together, in flashback.
As Swamp Thing blames Superman for a drought currently affecting his region, just by his presence. The Green was a concept initiated by Alan Moore and copied and referred to continually since. And the handprint?
…until he is able to learn how to change his electromagnetic frequencies to match the Earth again and return.
Because Superman… is of the wrong frequency.
Which is intriguing – this Superman is meant to be the old Superman, shunted sideways while the New 52 Superman took his place on the DC Earth, and has now returned. Wasn't that the consensus? Is he a parallel Superman after all?
Or is he Dr Manhattan?
Superman Annual #1 by Peter Tomasi, Patrick Gleason and Jorge Jimenez is published today.