I just got a new mass gainer, and my stools are sand tan, it has 10mg of creatine and also has tribulus in it, should this tan stool be a concern?

Not necessarily: If you are having abdominal pain or vomiting then you should be seen right away by a doctor to check your liver and pancreas. Studies show: Taking tribulus by mouth, alone or in combination with other herbs and supplements such as androstenedione, doesn't seem to enhance body composition or exercise performance in athletes. See your doctor for a more useful regimen.

Maybe not, but...: The gallbladder concentrates bile from the liver &mixes it with food to digest fats in your diet. When gallbladder is sick, you may feel right sided abdominal &/or back pain, +/- have RUQ tenderness. Liver disease or obstruction of bile ducts may result in jaundice,dark urine, tan-colored stools, pancreatitis. Consider stopping product & get help ASAP esp. if jaundice +/- persistent acholic stool.