The red on your '56 would have been the bright red & yes the black piping is correct on your seats. The white cars came with the option of red seats/black piping or black seats/white piping.
From the pictures of your car, there are a few incorrect items, the steering wheel should be black together with the steering shroud which should be crackle black - if there is no one near you who can do this, you can ship it to Omnicron in the UK, they are Lancia restoration experts and do wonderful crackle finishes on items. If the steering wheel is not cracked, ordinary brake fluid does a great job of stripping paint off plastic parts without damaging them. There should be no wood finish on the instrument panel either.
Beautiful Spider - what is the chassis & motor numbers and do you have more pictures
This is an archive picture of a '59 750D white with red interior -the extra matting on the floor is not original, it should be rubber mats & carpets just like George Kraus' car