I use a pink highlighter to repink!
This is a tutorial I made ages ago but I haven't posted it online in ages so here goes
What you'll need:
A pink highlighter pen, a piece of paper, some household paper and of course a pony with faded hair. Repinking a pony with highlighter can be a bit messy so if you don't want pink fingers, use gloves.
I like to start with the mane. Use the highlighter to paint from the forlock and down. Use the paper to protect the table. Turn the pony over and repeat until the entire hair is covered in pink.
CAUTION! Don't paint all the way to the root of the hair or it will cause permanent stains! The highlighter usually reaches that area in anycase when the hair is sucking up the color. If you get highlighter marks on the pony while painting you must clean it off straight away as it will leave unremovable marks. Use a cotton stick and some water or even acetone or nailpolishremover if it has started to dry already.
Same for the tail. Start at the root (leave space between color and root just as with the mane) and color it to the tops. It's easier to apply the color if you separate the hair into sections.
When the ponys hair is all pink you will have to let it dry. Use paper to wipe the hair as much as you can. Some of the color will come of, which is OK since it otherwise might stain the pony when you leave it to dry. After some time the hair will become stiff and icky as the colors dries. Personally I like to leave the pony like this for 1-2 weeks (or even more if you wish).
Rinse the ponys hair with water! Don't use soap or schampoo as this will most likely take the colors straight off. Any hair treatments to the hair like defrizzing should be done prior to the repink.
Done! Pretty pink hair