Tove Danovich writes about the Teal Pumpkin project on NPR.org:

Having a teal pumpkin on the doorstep (teal being the color of food allergy awareness) is a way to signal to people with food allergies that this is a safe home for trick-or-treating, says Jennifer Norris, president of the Food Allergy Community of East Tennessee (FACET), which started the project.

I learned about the teal pumpkins a couple years ago, and we have been a teal pumpkin house on Halloween ever since.

Since discovering that my children have peanut allergies, Halloween has moved from a fun tradition to an endless, irritating minefield of peanut-containing, and potentially peanut-contaminated, foods. (Practically every candy or baked good with chocolate may be contaminated with peanuts. As parents, my wife and I have to be very strict and diligent.) So much candy is off limits to my kids that it makes me feel sad for them. I think they do miss out on a huge, terribly unheathy part of the experience: the candy. We are baking some brownies and have purchased some truly safe, peanut-free chocolate for them, so Halloween will still be fun, even if the collecting candy part of trick-or-treating is kind of pointless.