The erasable pens are great fun to make patterns and designs over your colouring pages, to give them a personal customisation. They're also particularly useful for when you go out of the lines, as the eraser completely eradicates any ink that it touches.
Overall these are awesome for children but also a cool way of changing up your adult colouring pages to make them unique!
You can find these pens on Amazon here:
Fibracolor Magic & Erasable Pens