: There is no comparison of lemon juice to remove copper stains of any color. You can rub it with 3/4 drop of lemon juice or rub it with the said (cut part of lemon) without taking out the lemon juice. And if it is white cotton, then you can make it with lemon juice or bleaching powder, but if you apply too much, the copper will be ruined. Moreover, the shampoo is very effective. Apply to the stain with any shampoo and rub well. Then it should be washed well. Again you can wash with hand sanitizer. Apply hand sanitizer on the stain and leave it for about 1 hour. Then rub it and the stain will go away. Thanks.