My Dear Friend, First, masturbation is in no way harmful to health. You can do it daily, you can do it multiple times  in a day, it will have no ill efffect on your health. Red wine colour stool has nothing to do with masturbation. The colour might be secondary to some food that you had on earlier day or due to some bleeding in the intestines.  suggest you get a routine examination and occult blood examination done for your stool at some good pathology lab. Dr. Anamay Kamalakar Bidwai Chennai