While it's not a dead giveaway, I've noticed aspies tend to trend more towards clothes which are picked more for comfort than for external appearance. There was actually one guy I worked with who had a lot of 'tells', and one of them was that he had an entire (workplace) wardrobe which looked like business casual to a quick glance, but which closer up revealed itself to be all very soft, comfortable materials. And it was almost all in monochromatic shades of grey or black. I actually really liked it as a personal style.
This isn't to say that all aspies dress the same way. But dressing for internal tactile sensation rather than the social impression on other people does seem to be more common.