I also love the grey-scale costumes I've seen (you wear all black, grey and white outfits and spray your hair black or grey and put grey or black makeup on all your exposed skin so you look black and white). That wouldn't be good for kids, since I don't want them to rub makeup on everything they touch, but maybe for me and Jason.
In the meantime, here are two outfits with a bit of color:
The twins from The Shining
Little Edie from Grey Gardens
Ruth Bader Ginsberg
Grey tank, yellow cardigan, navy cords and grey boots. I like how this yellow sweater really stands out against neutrals.
Have fun if you're trick-or-treating or going to a party tonight!