For some reason, the blue dropped out on several (non-consecutive) pages of this Golden Age comic, putting Superman (and Clark Kent too) into a white suit as he flew around white skies, over yellow foliage, across three different stories. So we CAN'T blame Mr. Mxyzpltk for this one, because he's only in the first.
And I don't think there's any truth to the metatextual explanation that there's some Divine Colorist who, on a whim, can alter Superman's reality. The comics company wasn't even called DC after such a being back then. And He certainly isn't being evoked in the this panel:
I guess sometimes a guy wants to impress with some cool new duds he got down in Panama, or something.
So however you explain away the anomaly in-story - and you can't because the suits keep changing back and forth between pages - the million-dollar question is: Was this the inspiration for putting the "S" on a white shirt in Morrison's Action Comics? On Bruce Timm's Supergirl before that? For White Lantern Superman? Or for the Fantastic Four's current look? I know MY answer.