shingles

Get several different full sized sample boards of each one and compare it to your siding color.

If they are really that close though, it probably doesn't matter and you are overthinking the decision.

Also, ask if the roofing contractor has any houses with those colors installed on them and go take a look at an entire home.

Ed

The colors from one manufacturer to another differ because they each use a tad bit different blending procedure to produce the same color.

In my area we have two shingle supply houses that have fairly large display rooms for home owners to view large samples, but the best way to go is like Ed said, find homes in your area with that color on them.