Pinky McLadybits
Pinky Jr. decided that she wanted purple and pink hair. Being 7 years old, I wasn't about to bleach her hair and then apply the colors that she wanted, which took care of a few options. Also, her hair is red like mine, which means it can be difficult to get a big color change to show up.
Or at least, that was the problem when I wanted purple hair. Since I was already at an appointment with my stylist at Ulta, I asked her what she recommended. She told me that there were washable pens, but they didn't carry them. But CVS had Splat Washables haircolor in purple, pink, blue, and dark red. Since they were $6.84 a box and I wasn't sure if they would work, Pinky Jr. had to choose and she went with purple.