Later this year, when the popular statin Lipitor becomes available as a generic drug, many who have taken it faithfully will get a surprise. No longer will their cholesterol-lowering pills be oblong and white. If they choose a generic alternative, their pills will be anything but that color and shape, and their appearance may change from refill to refill as pharmacists switch among generic competitors. The result may well be confusion among patients, who often take multiple drugs and have trouble keeping track of them if their shapes and colors change all the time, two researchers at Harvard University say. With generics accounting for 70% of all drugs on the market, the seldom-discussed issue of their ever-changing appearances affects almost anyone who fills a prescription.