DD is 3 weeks old. she is the absolute double of DS at that age.
When he was wee, people would always comment on a what a little boy he was, how masculine his face was, how you couldn't mistake him for a girl etc etc. I tended to dress him in blue if it was to hand, but he had a lot of white, red, stripy clothes too.
Now DD is getting the same comments, except they are all 'ooh, what delicate features she has', obviously a girl, what a feminine face! She is also dressed in fairly neutral clothes, some blue, some red, some pink, depends what she hasn't chucked on that day.
So why do people do this? Both babies, IMO look like babies, and you can't tell from first glance what sex they are. But even my parents, who keep saying how she's the double of DS, have been saying what a little girl she is 
is it just politeness because there isn't much you can say about a newborn?