mmmm, my own take on this is that if selecting a brown finish, you should consider a uPVC that is also brown underneath. The grain is usually just a film applied to the outside. I've heard that at joints, if it's not perfect, or if it shrinks, the underlying uPVC becomes visible. If it's white, you'll see......er, white !
OTH, do you want wood colour on the inside too??
I got grey wood-grain outside, white inside, from T.J. O'Grady's in Co Mayo - they were the only people who would do what I wanted.
p.s., oh, and you don't want Swedex !!