OK, I feel like a tool, because when Winslow chose a pink Deluxe Boy body, I just assumed that meant he was gay, because Pink On Men Must Mean Gay, and not just because, y'know, it's a nice color.
As it has been mentioned already I will help put to rest the misinformation regarding colour then and now.
(Brevity)
The meaning of colours has changed. One thing all of these explanations lack, however, is an appreciation of local variation, and different meanings being attributed to different shades of one colour. And that's not even touching on the duality that was attributed to most colours.
White, for instance, was death, as the colour of bleached bone - and for a long time stood as the opposite of red, for blood. At the same time, it was the colour of purity: take natural linen, and white is your most dependable colour, no matter how many times you wash and bleach it.
The meaning changing also shows in pink, at a certain period being very firmly associated with violence, and crime. It's not entirely implausible that the connection with homosexuality stems from there, as at that time, making the villain gay just served to add a layer to his villainy.
Blue for girls, on the other hand, has a firm root in mariodoxy, white and blue being the colours associated with the Virgin Mary.
Earth tones, grey, and black were most often connected to humility, and seriousness. There's a connection to the theory of humours to be found there, as well.
But there's no hard and fast rule. Red and blues were simply more easily available, for most of our history.
I do want to note that the notion of differentiating dress between boys and girls for young children, is a relatively recent notion. And up until the age where they would be dressing for their gender, children often went in white, for the simple reason that any accidents could easily be bleached out.
Saying girls had no value, is also doing a great disservice to large periods of our history. Another vice of the Victorians, was to reinterpret history, even their own, to conform to their own mores and expectations. Medieval studies are only now recovering a more balanced view of those ages, though in many ways, it's still an uphill battle against the Victorian myths that have very heavily influenced the popular image.
Edited for spacing.