Why the change of outfit? is an article in Resident Evil Recollections. It was uploaded on 3 December 2014.
Claire's memorable outfit from Resident Evil Code: Veronica features a red vest with a Valkyrie. She gave her other vest to Sherry in Resident Evil 2, so that might be one reason.
In Resident Evil Revelations 2 Claire is all grown up now, so her outfit has of course changed again.
To celebrate her return we've prepared a special chronology featuring Claire's most important events in the series, go take a look!