Try wetting a sample and putting it against a dark background (light may be bleeding through) as this will show the color it will be when finished.
Walnut also has pale sapwood. You will probably need to dye the wood in this case, to even out the color differences between the sap wood and heart wood strips.
Advice on getting a more even finish in walnut is here
https://www.youtube.com/watch?v=0EjIjCvxVGIMe personally, I decided to stop trying to match the wood on my models with the wood on the real ship. Why? Because the grain does not scale down. This is one reason why box/lime wood is popular, as it has a very fine grain. Colors can be matched with stains or colored varnishes. Box wood, and softwoods are also less brittle and easier to work with.
But that is just my personal decision.