That's the best choice if you are trying to match the existing paint (partial paint job). The original colors have surely faded over time. But if you are repainting all the cladding, it won't make any difference if its two shades different.
Probably a bit late for my comments now, but most paint shops have an electronic paint scanner. It will take an actual picture of the paint up close, and then give you the closest formula that it finds. Could be a different manufacturer's paint code, but it will be very close.
I used to do paint touch up work commercially years ago, and I know the scanner works.