It's easy to do: forget the cap on a pen, lay it down, and all of a sudden, there's a disastrous stain on the cotton blanket. At that point, you have only three options. The blanket either can be thrown away, the stain can be ignored, or the stain can be removed properly. Since most people don't want to toss away otherwise good blankets and want to keep things aesthetically pleasing, the best bet is to go with the third option and get the stain out.
Basic Removal Method
Try the basic method of removing stains from cotton before proceeding to more drastic stain removal attempts. First, remove the excess ink by blotting the stain with an absorbent material, such as a paper napkin or towel. If you don't do this, you'll be putting your treating agent on the extra ink rather than on the ink that is held in the cotton fibers. After blotting, apply hairspray to the stain, let the stain sit for a minute or two, blot again, and repeat until the stain comes out.
Treat the stain as soon as possible, preferably while it is still wet. This will keep the stain from being set into the cotton fibers. If you cannot treat the stain right away, at least put the portion of the blanket with the stain in a sink or bathtub with some water to keep it from drying out until you can get to it. Another option is to put a stain removal product directly on the stain until laundering.
When you launder the blanket, don't use hot water, as this will cause the stain to set. Instead, use a cold or warm wash. When you dry the blanket, the same principle applies. You should use the lowest setting on the dryer or simply tumble dry. Hanging the blanket outside to air dry is even better.
Although hairspray works quite well to remove ink stains, you may also use swabbing alcohol or fingernail polish remover on the stain or scrub the stain with a paste of baking soda and water. Keep in mind that some chemicals for stain removal may bleach out color, so don't use any agent unless you know how it reacts with clothes. As a last resort, you may have to take the blanket to the dry cleaner.