DD is 5 (nearly 6) she is a pretty girly girl in some ways - she likes dresses, and shoes, and sparkles - so she is not immune to gender stereotyping but I have done my best to convince her that there are no boy colours or girl colours. That if she likes something she can bloody well have it regardless of hue or location in store.
As a result her sparkly dresses are generally green, and accessorised with monsters inc headwear and wolf feet with claws (because she's very into monsters alongside her penchant for fairies) which she picks herself from the 'boys' section of the shop.
The other day I was evesdropping on her conversation with one of her little boyfriends and he told her that blue is a boy colour.
She got a touch of The Rage and told him "that's stupid!"
Colours are for everyone"
I had a little rush of smug pride at her forthright behaviour and refusal to back down
AIBU