A very common nail disorder is nail discoloration. This can be caused by many different factors like poor blood circulation, a heart condition or from various types of medications. Nail discoloration that is yellow can be the result of keratin build up under the nails. There are medications that help with the latter disorder that will dissolve the keratin and revitalize your toe nails. If other heath problems are causing the discoloration, after speaking with your physician for suggestions for the discoloring, you can use nail polish or artificial nails to cover the discoloration.