De Nimes is one of those gorgeous washed-denim blues — soft, slightly greyed, brilliant in a hallway or as cabinetry. But you're paying F&B money for it, so let's find you something honest.
The nearest match by a country mile is Crown Dark Grey (LRV 19.9), measured at just ΔE 2.8 from the original. That's inside the "very close" band — on a wall, in real light, you'd struggle to tell them apart. Crown's a proper trade-grade paint at a fraction of the cost, so this is the one I'd reach for first.
Next up, COAT Mr. Clifton (LRV 23.5) at ΔE 3.5. Slightly off the F&B original but a lovely thing in its own right — COAT's a low-VOC, water-based modern brand with cracking coverage, and Mr. Clifton has that same denim character. If you care about eco credentials and a velvety modern matt, go here.
I'd steer you away from Dulux Denim Drift (LRV 26) for this particular job — at ΔE 5 from De Nimes it's a noticeably different, brighter and slightly more blue colour. Denim Drift is a smashing paint and was Dulux's Colour of the Year, but it's not actually a De Nimes dupe. Don't let the name fool you.
Note the LRVs are all in the high teens to mid-twenties, so this is a deeper, characterful blue that wants decent natural light or it'll go quite dark and moody after dusk. That's the whole point of it, mind — lean in.
Practical advice: buy a tester of both Crown Dark Grey and Mr. Clifton, paint two coats on a bit of lining paper, and move it around the room over a day. ΔE figures get you to the shortlist; your own eyeballs in your own light make the final call. For trim, keep it simple with a soft white in eggshell.