Hi and welcome to Healthcaremagic. Thank you for your query. I am Dr. Rommstein, I understand your concerns and I will try to help you as much as I can. Well, this is not surprising for hormonal pills intake and the cause of yellowish or brown vaginal discharge is common and usually harmless issue. Occasional spotting between periods might have this appearance at the beginning of pil use. So in most cases this is not sign of disease. Less common,it may indicate bacterial vaginosis, STD or polycstic ovarian syndrome. Occasionally some other hormonal disorders may be present. In some cases, however, a yellow or brown vaginal discharge could indicate a serious problem. Although brown and yellow 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 then you should see gynecolgosit for further work up. In some cases, a yellow or brown vaginal discharge could indicate a serious problem. Wishing you good health. Regards