A suffusion of yellow
Assuming that Rogue was say 14 or 15 when she has her first kiss, she ran away and then spent time with the Brotherhood of Evil Mutants, if we assume that was maybe 4 years she would be 18 or 19 when she seeks help from Dr X.Rogue's powers manifest when she's a "young teen". She kisses a boy, gets understandably freaked out, and runs away from home. She then takes up with Mystique - the term used in the comics is "adopted". That's not a term you normally use with an adult - so I find it hard to take her as 17+ at that point.