I'm a teacher and I teach kids of this age. Kids this age more likely to speak out, pass comment or ask why if they see something different, and I do get kids asking me, why don't I do this, or like that, because they think that because most people do something, that everybody has to do it. A student asked me why I wasn't celebrating woman's day, and I told her that celebrating it was optional, not obligatory, that means that people celebrate it if they want to and don't have to, and if they don't want to, then that's ok. If it were an older kid, I would say that I experience being a woman every day and I don't need a special day to remind myself of the fact, or to remember that half the planet's population are women and that they have equal rights, etc.
Sometimes they ask me why I do something or don't do something they think I should be doing, or why I am like this or like that, and I just say "because that's the way I am" or "because that's how I was made". I don't have to justify myself, why I am as I am, people are all different and that's that. It's good for kids to realise that people are all different and that we don't always have to do things just because everyone else is doing them, we have a choice to do them or not to do them, there are all sorts of different people on the planet with different opinions, lifestyles, etc and that's ok.
So, I would just go as you are, wear whatever colour you want, and if any kid does ask you why you aren't wearing blue, just say that wearing blue is optional, you don't have to wear it if you don't want to, you prefer red to be for autism, and anyway, that's what autism awareness is about - being accepted as different and not feeling shame for being different - that you are different because you are wearing red instead of blue, and you are proud to do so, people being different should be accepted and not judged and that is how you choose to raise awareness for autism.
