Find one that matches your garment exactly, otherwise, it will stand out as much as the stain itself! Cover over the stain with the marker, and set it with an iron, or put it in the dryer for a few minutes to make sure the ink doesn't run.  Always test the marker on a rag or old garment first to ensure you have chosen the appropriate color. This works great for black and dark colors, but not so well for whites and light and bright colors. Sometimes it can be better to work with the stain rather than against it. Begin by washing the garment and placing it outside in direct sunlight. Wait several hours and repeat the process if required.  Ultraviolet rays are bleaching your garment, ensure the garment is placed flat with no wrinkles. You want it to lighten evenly. This method won’t make the stain go away fully, but it will help to lighten it. It is a slightly more drastic measure but can be very effective to change the color of the rest of the garment. Add your garment to a large bucket or basin of water, then add a capful of bleach. Swirl the garment around in the bleach mixture until your desired color is reached, adding more bleach as required. Rinse the garment and then allow it to soak for half an hour in a bucket or basin of cold water and hydrogen peroxide.  Add 50 grams of hydrogen peroxide to every 4-5 liters of water. Treat bleaching the whole garment as a final option once you have tried natural remedies and less invasive chemical options.
Use a permanent marker to fill in the stain. Try the sun-bleaching method to lighten clothes naturally. Bleach the whole garment as a last resort.