No, it's your house so you can go with whatever you like, but the more cohesive it is, the better it will look. And the happier you'll be down the road.

Hayley is correct. I would suggest you stick with the same SPECIES of wood (white oak or red oak) and then have the upstairs stained in your choice of colour. That means in the future, should you WANT to have all the floors match, you have the ABILITY to produce a very easy match.

Different species take stains differently. If you keep the species you keep the ability to get them to match using the SAME STAIN at a later date. It makes life easier.

If you want a different look upstairs, go for it. This is being done quite a bit. Simply put some thought into working with the same species and then staining to get the look you are after. You will be glad you did.