My almost 4 year old DD is currently ignoring messages from her friends about what colours she's 'allowed' to like. This is the very small tip of an iceberg, I know, and may seem trivial.
How can I help her as she meets this sort of thing more and more often? She's quite 'young' socially and couldn't care less what anyone thought of her at the moment. I'm sure this will change. Right now, she says, 'that's silly, I do like blue', or similar.
I'm not sure there's anything in particular to read, but I do think you can work with the assumptions. For example, I know eventually DD1 is going to get into the whole princess thing so I am trying to steer her towards princesses who are active so I have been reading mm Kaye's The Ordinary Princess and am trying ti get hold of the paper bag princess.
If she is saying 'that's silly, I do like blue', just encourage her in that. You could mention how sad it is that some people limit themselves and how wonderful it is that she isn't doing so.
Hope that helps a little bit. But I should say DD1 is only two so I am talking theoretically here.