Hi, Well, the cause of grey vaginal discharge is common and usually harmless issue. Occasional spotting between periods might have this appearance and can be normal, especially if you re taking low-dose birth control pills. So in most cases this is not sign of disease. If it is, then usually this indicates bacterial vaginosis, STD or polycstic ovarian syndrome. Less common, some other hormonal disorders may be present. In some cases, however, a yellow or brown vaginal discharge could indicate a serious problem. Although vaginal discharge often does not indicate a serious problem, it should not be ignored if it persists, recurs or is accompanied by other symptoms and you should see gynecologist for further work up. In some cases, a yellow or brown vaginal discharge could indicate a serious problem. Hope I have answered your query. Let me know if I can assist you further.