If you really wanted to mix I would do the 4 panel and the 1 panel. I don't think the 2 panel would go with the 4 at all because they are both "busy" in a sense. If one was busy (4 panel) and the other more plain (1 panel), I feel it would match better. Personally, I wouldn't mix door styles but it really all depends on personal preference. I went with a 5 panel equal shaker for all my doors. In our bedroom the entrance door is a solid 5 panel shaker but the walk-in closet and ensuite doors are 5 panel shakers with frosted glass. That's about as much mixing and matching that I did. Don't you wish you could borrow doors from the store for a day (like you can with flooring) and see how it would look? I had a hard time deciding between the 3 panel equal shaker and the 5 panel equal shaker. I ended up going with 5 obviously but it was a tough choice, especially not being able to see them in action. Good luck!!!

Its absolutely fine to go with a different door style. A real colonial/early american 19th c. house often has different doorstyles throughout anyway, ranked on whether the room was "public" or "private", first floor or upper floors, or even by importance in the same room.

I would say colonial style and scandi go well together. I disagree strongly that you should keep to the original style of the house. However, as a designer, I would say different ideas look better together if they share some similar characteristics or are related - as colonial and scandi are. I think there some degree of lightness and openess in both style, turned wood in both scandi and colonial furniture, although lighter wood and white in scandi. With a keen eye and careful research, two styles that share some common denominators can always work; otherwise you risk looking like a museum otherwise. I would not mix tudor and scandi for instance or high victorian english, as they are diametrically opposed, but if they share components, go ahead.

Matters NOT. WHAT MATTERS IS does your hardware selection, the door stain or color or the hardware on that door in both style and finish...........suit the door itself, and also the exterior of your home. We certainly don't know that. Do we?