I, personally, would order the windows in white. Not only will they go with your interior trim color choice, but white will probably look "cleaner" with the ivory outside.

Two tone vinyl windows are made. There is an up-charge for that option. The two tone option is sometimes difficult to match to existing trim coils.

I would encourage you to stick with the white.

We just built, have white vinyl windows and cream trim. It looks fine and I have to admit that I am picky. Plus, you'll likely add blinds etc. My blinds are pure white as well and look fine with the cream trim.

Now subway tile in the kitchen with cream cabinets is a different problem. There, I think you match the trim and go cream.