Composites often change color substantially as they age, for example
the "gray" Trex starts out as a reddish brown and "grays" in 3-6 months
of exposure to full sun, you purchase these materials based on the
final result you want - in my experience the eventual result is usually
quite uniform, and and pretty close to the result depicted in the
manufacturer's brochures.

BTW, one thing to watch with a lot of these materials is salt applied
to decks and stairs in winter conditions- some of these materials will
stain baldly, the stain extends some distance into the material, and
I'm aware of no way to remove it.

Michael Thomas
Paragon Home Inspection, LLC
Chicago, IL
mdt@paragoninspectsDOTcom
847-475-5668.