Preservative/stain for feather-edge boards

[silentbrown]

We had this re-treated in summer '24. I'm not entirely sure what was used, but the lower edges of the boards are already fading towards grey. I tried some generic 'dark oak' stuff as a test below the security light but as you can see it's far too pale/orangey.

What's the best stuff to use for this, and what's your best guess for a good colour match?