Paint pens are useful for colouring objects that cannot be written on easily with normal pens or markers. For this reason, paint pens are sometimes used to touch up paint or scratches on cars. If paint pen was applied to your car in a colour that doesn't match properly or was applied too liberally, you may want to remove some or all of the paint.
Wet a melamine foam pad and wring out the extra water. Magic Erasers are made by Mr. Clean and Easy Erasing Pads are made by Scotch-Brite. They are made of a foam that acts as a super-fine sandpaper that can clean many stains such as paint, marker and crayon.
Scrub the paint pen stain with the Magic Eraser or Easy Erasing Pad. If the eraser cannot fully remove the stain, move on to Step 3.
Apply rubbing alcohol to a soft cotton cloth and rub the paint pen stain with a circular motion. Press down hard to allow the fibres of the cloth to rub the alcohol into the paint.
Wash the area with some water and assess the stain; if it is still there, move on to Step 5.
Apply hairspray to a soft cotton or microfiber cloth and rub the paint pen stain.
Repeat any of the three washing methods if the stain remains; try rubbing more vigorously to get the stain to come loose.
Some people recommend nail polish remover for removing paint, but this might cause damage to the clear coat or other paint coats. Paint can be removed with fine sandpaper and a buffer, but that will take off more coats of paint and require repainting; your goal should be to remove the stain with as little friction as possible.