Green nails can be caused by Pseudomonas bacteria, which grow under a nail that has partially separated from the nail bed. This infection may cause a foul odor of the nails. The treatment is to trim the nail short every four weeks, don't clean it, polish if you want to hide the color, and wait two to three months. It is also advised to avoid soaking the nail in any sort of water (even if inside gloves) and to thoroughly dry the nail after bathing. If the problem continues, there are prescription treatments that your doctor may try.
Toenail fungus is an infection that gets in through cracks in your nail or cuts in your skin. It can make your toenail change color or get thicker. It can also hurt. Because toes are often warm and damp, fungus grows well there. Different kinds of fungi and sometimes yeast affect different parts of the nail. Left untreated, an infection could spread to other toenails, skin, or even your fingernails.