My thoughts on the design:
First Superman’s look is iconic, so I didn’t want to veer too much away from how he currently looks. In a way this is only a slight variation of his present representation. My thought always about Kryptonian society is that they are sort of what we perceived as a Romanticized “Roman Culture,” which is about honor and pride. I always envisioned what Superman is wearing as a Kryptonian fashion rather than a design of Ma Kent's.
I made the cape more billowing on the shoulders. In my mind it sort of signifies the house of El’s prominence is their society.
The primary colors might also signify their simple and down to earth attitude, even though they are held in high regard, this might explain Superman’s nature.
The other alteration is the boxers, as much as I want to remove it (no guys! not in the way that you are thinking) because that is always a reason to ridicule Superman-- again it is a big part of his iconic costume. Removing it alters the character drastically. So my idea was to integrate it into his overhaul. Now it is more of a design, a breaking in colors than an actual undergarment worn the wrong way. I made some slight changes to his belt or the lack of it. Again it is just part of his costume, some sort of Kryptonian “bedazzled” though it is functional.
The last thing I tinkered with is the shield. I felt that this is a coat of arms from the house of El. Superman wears this because he is proud of his heritage. My only qualm about the shield is that it looks too much like an “S” rather than a Kryptonian symbol. I came up with this design for a symmetrical look, which I think compliments an advanced civilization. It could still be mistaken as an “S” but this time I feel it is more Kryptonian.
Here’s an Anime’ look for Superman: