My Stool Was Green And Grey, What Does It Indicates ?

Last time I went to the bathroom my stool was green and grey. Not a mixture of the two, but some parts were green and others were grey, almost white. What does this mean? I m a 27 year old female. Was just at the doctor due to unexplained weight loss , and he told me I was healthhy. He ran blood tests and took a stool sample. I m on the generic form of welbutrin(spelling?) and also take vitamins daily. I m 5 3 and weigh 103 lbs. I recently lost about 15lbs. I don t know why, I eat the same I always have. My doctor said it s probably stress/ depression . I do have chronic night sweats as well. Wake up soaked almost every night. Other than that I ve always been healthy. Cancer does run in both sides of my family. My mom passed from it. All 4 grandparents had a form of it, and 3 other of my aunts and uncles have had it.