Some people call colours different things. For breeds that only have one colour recognized it's called standard in most software, but some people prefer to list what standard colour actually is, so it appears you're software gives you that option.
The software I have for my pedigrees, under the Mini Rex I have the option of putting White, or Ruby Eyed White. In Mini Rex REW is not called REW it's simply called White, but that confuses some people because White can also be BEW (which is listed). So some people instead of using White for a REW Mini Rex will just put REW to cause less confusion.