Summarize this article in one sentence.
Use the handle of a rattail comb to part your hair right in the middle, from your forehead all the way down to the nape of your neck. Harley Quinn does have messy hair, but you will do that at the end. Keep things neat for now. The pigtails need to sit right on top of your head, above your eyebrows and behind your ears. Use a comb or brush to smooth the hair down as much as possible. Leave a 1-inch (2.54-centimeter) strand of hair hanging loose on each side of your part. Hair chalk can be applied to wet or dry hair, but it will be brighter on light hair. If your hair is dark blond, brown, or even darker, the hair chalk won't show up very well if you apply it to dry hair. Mist your hair down with a spray bottle filled with water, then comb it through. You only need to dampen your hair about midway down. You will need to use bright blue for the left pigtail and light pink or red for the right pigtail. Start adding the colors about midway down. Work with 1-inch (2.54-centimeter) wide sections.  If you damped your hair earlier, let it dry before moving on to the next step. This step can get messy. Consider putting on an old shirt or draping a towel around your shoulders first. If you don't do this, the chalk will rub off. Be aware that some color may rub off onto the heat tool, however. If you are using a hair straightener, twist it while straightening your hair so that you get loose waves instead. If you are using a curling iron, try using a larger one instead to get looser curls. This will help set the chalk into your hair and prevent it from rubbing off. If you don't have a hair straightener or curling iron, you can mist it with hairspray. It won't work as well as a hair straightener or curling iron, but it will be better than nothing. Take a strand of hair from the underside of your first pigtail. Wrap it around the base of the pigtail to hide the elastic and weft. Secure the strand of hair with a bobby pin. Repeat this step for the other pigtail. The colored strands will give the illusion of a colored hair tie. Try to finish wrapping the hair strand on the underside of your pigtail. You can also use a wide, satin ribbon instead. Secure it with a strip of double-sided tape instead of a bobby pin. Use blue for the left pigtail and red for the right. This will give you a messier look. Only backcomb from the middle part of the pigtails and down. Be sure to focus on the ends of your hair where the hair chalk is. This will help further seal in the color and prevent it from coming off.

Summary:
Brush your hair and part it down the center. Pull your hair up into high pigtails and secure them with hair ties. Dampen your hair if it is dark. Rub hair chalk into each pigtail. Seal the color in with a hair straighten or curling iron. Wrap strands of hair around the base of each pigtail. Backcomb the pigtails. Set the style with hairspray.