When you have 3 little kids, and are chronically underemployed, everything you do has to be low cost and high concept; halloween costumes are no exception. My wife participated in The Color Run 5K a few years back, and it looked fun (except for all that pesky exercise). How could I be a Color Runner without running? You guessed it: trick or treat! The 1st (and most important) step is the colored powder.
COLORED POWDER RECIPE
1 cup corn starch + half cup of water creates a weird substance called oobleck, which has properties of both liquid and solid matter. Use a strong food processor to mix it (it will fight you), then add a whole tube of food coloring to it, spread it on a cookie sheet, and let it dry out for 2-3 days. For further drying, preheat oven to 350, shut off oven (very important), and place crackly, dry, colored remains into oven for 10-20 mins. Use a magic bullet or similar device to pulverize into powder. Keep in zipper bags until needed. Cornstarch was $1.25. One small box was enough for 3 colors (3 cups), which can cover a family of 4-5 easily. The food coloring we already had.
Go to your local thrift store and purchase white clothing. We only spent about $5 for the 3 pieces we needed. The rest, were old, stained, or worn out white clothes we already owned. If it's cold where you live, spring for dollar store hats, mittens, etc., too. Dollar store purchases were about $6
I created our Color Run logo to match the colors of our powder, using the actual logo as inspiration. I designed it in Adobe Illustrator, but any program will do. I laid out several different sizes onto a letter size sheet, and printed onto iron-on transfer paper, using a standard inkjet printer. Make sure to reverse your design, or it'll be backwards on your shirts. I used the smaller logos for the dollar store hats. We already had the iron-on transfer paper.
Once you've ironed on the logos, you can gear up and head outside (you definitely don't want to get colored powder all over your home). Grab little clumps of the colored powder and have fun pelting each other all over, until nicely covered. Plan to head straight to baths/showers when you return and have a hamper ready. We took TWO 2 year olds, a 4 year old and a 2 month old baby with us; much fun was had by all. Total cost: $11
WARNING: I don't recommend this costume for visiting a friend's home or taking a car ride, as you will spread more dust than Tinkerbell.