I would choose the red. Natty's red has a very nice look to it. It is a little improvement on the looks of the blue, more of that carnauba glow. Plus it is incredibly slick and a little easier to work with than the blue. Natty's blue is great and Natty's red is another step ahead of that.
As for the Liquid Souveran ... it has its place, you'll find LS to look better on light colors vs. dark. The liquid Souveran doesn't darken or look like the regular Souveran. Seeing you'll be using it on a Red Silverado I think Natty's Red would be a good choice

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