I encourage them to be unique... why not?! Can't hurt anybody. My 7 year old especially, she is very outgoing and opinionated and doesn't care what anybody thinks of her 'style'. She gets a lot of more adult humor, and can give it right back! She's a total tomboy. She doesn't care. She loves wearing camo pants, white t-shirts, climbing trees, getting dirty, sports... but then she'll go and put her hair in pig tails to give it a bit of feminine flare. She 'gets it' ;)
My 5 year old is a princess diva supreme. She's always wearing pink or purple and loaded with costume jewelery. People try convincing her all the time that she's too old for the princess stage... um, she's one of those kids that will NEVERRR outgrow the princess stage! She was born a princess, LOL!! She won't leave the house without her nails done, LOL... and she's constantly in pink tutus and sparkly slide on shoes.
My kids aren't Autistic, but like you guys, we're all pretty quirky. We're definately 'the odd man out' at school functions... but we're all likable enough ;) No harm, no foul in letting kiddos embrace what they like, whether it's a phase or not ;) I bet Andy rocked that suit ;)