Why would someone born in the late 1980s in a universe without Superheroes (or at least without Superman) adopt a costume based on circus outfits from over a hundred years ago?
Where does this 'indigneous' hero outfit come from?
And whilst we're at it, how can he fly?
I just think that it's much more satisfying on pretty much every level for 'Superman' to be the living embodiment of the things that young Clark would have perceived as 'super' when he was a child ie. comic heroes, strong men etc as opposed to wearing what appears to be Kryptonian long johns (as Samurai8472 pointed out.)
But again why would a kid in the 1980s/early perceive 'strong men' to be 'super'? You might as well say it is because he loves "I love lucy" - if you want to go down that road.. you'd be better off saying he based the colours on watching Optimus Prime on the transformers cartoon.