Hello, Welcome to Healthcare Magic. I have read your question fully and understand your concerns. I am assuming the part that you described as the outer part of the vagina is actually your vulva/labia (lips). It is common and normal for the labia/vulva to be darker than the rest of the body. Either the whole of the vulva can be uniformly darker, or just the lips could be dark. Either way, this is normal. How was your vulva three years back? If it was not dark before, the discoloration could have occurred now. There are some contributing factors to dark genitalia - use of hygiene products/creams, frequent shaving, hair removal creams, use of harsh soaps/talcum powder, wearing tight inner garments and clothes. If you have increased your weight lately, this also can cause dark vulva. Unfortunately, as there is no direct way of examining you to reassure you, can I suggest you to kindly see doctor and get yourself examined? I hope this answer has helped you. Thank you Regards Dr Sunita Sayammagaru