I have seen the same thing. My daughter was born 5 weeks ago and I think her salmon patch looks brighter/redder than it did at birth/in the days thereafter. It is very prominent. I think part of that though is that she was a bit jaundiced for a couple of weeks so now her skin is much fairer than before, and the contrast is more obvious. I could be wrong.
My understanding is that they don't start fading until a few months at the earliest. I think they should fade more significantly after a year or two.
Is that right?