Barbie is clearly aimed towards young girls, which is why the colour of the logo is pink. I've changed it to the colour blue, which is seen as a "boy colour". Just changing the colour to blue has made it look less "girly" and more ambiguous. This is exactly what Barbie (as a company) does not want. It's too confusing and doesn't make it obvious who the target audience is.
Barbie has a specific audience to market to, which makes it easier to choose colours. But what if there isn't any clear target audience? For example, Facebook, this is used by millions of different people from different backgrounds and cultures.
Click for larger image
To be honest, changing Facebook to green hasn't really done much. It does look more 'earthy' and fresh. However, green like blue is quite a neutral colour.
I've made a few other colour changes to famous logos. Click for larger images.