This is a rear, rhs NOS fender beading in one of the various shades of white. We are not able to tell which one exactly, they could be yellowed as well.. For a notchback!
Please also note that a good painter can paint fender beadings in the color of the vehicle. If the right nuance or color is not available either, you can have it painted. We have already done this on some of our showcars.
When installing, they should be warmed up with a hair dryer, or be sure to install them in a heated garage or environment. This helps immensely during installation!