Multiple bedding questions

[hopkins_student]

So I recently bought some Frette sheets. I was expecting they would be nice, but I didn't think I'd end up liking them as much as I do. I bought a sheet set which is very slightly off-white ("ivory") with a blue decoration near the top of the flat sheet and also near the edges of the pillowcases. I intend to buy one more sheet set as well as a duvet cover and the pillows required to make a complete bed. Now, however, I'm faced with a dilemma. I'm starting to think that I'd prefer a set that is of the same pattern, but which is truly white rather than off white, and has off white in place of the blue of my current sheet set. I also already have a duvet cover (non-Frette) which goes pretty well with the ivory/blue sheets but doesn't match perfectly.

So, I have several options:
1. Buy another set of ivory/blue sheets and ivory/blue duvet cover and have only one complete bed look. This would mean that the non-Frette duvet cover would almost never receive any use.

2. Buy the white/ivory sheets and duvet cover and use the non-Frette duvet cover with the ivory/blue sheets, for two different bed looks.

3. Buy the white/ivory sheets and duvet cover as well as an ivory/blue duvet cover, for two different bed looks in which the sheets both match the duvet perfectly.

Which would you choose if price somewhat matters but is not, in and of itself, a deciding factor?

Also, in choice 2, would it be acceptable to use primarily ivory sheets with a primarily white duvet cover?

And lastly, for now, does anyone have any hesitation about using a sheet which is primarily truly white? I've heard that when certain off-white bodily fluids make contact with truly white sheets, regardless of how well you wash them the sheets take on a yellow or off white appearance.

Thank you in advance for your opinions, H_S.