Neither discoloration of the penile skin nor erectile dysfunction is a sign of any STD. There are many causes of both problems, but the skin problem sounds like vitiligo, a disorder involving loss of pigment cells in the skin. Vitiligo can occur anywhere on the body; to my knowledge not especially common on the genitals In any case, both that and the erective problem are outside my area of expertise, which is limited to STDs. So I really can't help, except to suggest you see your primary health care provider.
Best wishes--- HHH, MD