Mississippi ain't red, it's mud brown. The Minnesota might be blue, but it too is probably mud brown.

I remember seeing an aerial photo of the Minnesnoter/Mississippi confluence a while back, and there was quite a difference between the light, muddy Mississippi (even just south of Minneapolis) and the much darker and bluer Minnesnoter. You could see the swirling as the two quite different flows mixed, Albeit the Minnesnoter isn't as clear blue as a glacial lake or some pristine Pacific coral sand beach....

Cheers,