Striped stair carpet

[HaveToWearHeels]

I live in a new build house, with a large hall which has cream polished porcelain tiles, the stairs to first and second floors, the gallery landing and all the bedrooms have cream carpet, which has got really grubby on the stairs to first floor. I quite fancy replacing it with a neutral striped carpet. Would I get away with just doing the stairs or do i need to do the landing to ?. Also what about the second staircase (which is not directly off the first and is still like new) would that need doing ?. Your thoughts please as I am undecided.