Why do we say "a one-legged man", with a final "-ed", but also say "a one-person job" without the "-ed"? We also say:
A two-minute walk.
A six-hour flight.
But then we say:
A green-eyed woman
When I think about it, it seems to me the pattern with a final -d/-ed suggests the idea of having, as in having green eyes. But this theory doesn't seem to work with some other compound adjectives like:
A two-storey building
It should be two-storeyed because it means made of or having two storeys.