Card Room Green is one of F&B's best mid-tone greens — that smoky, grown-up olive that works brilliantly on woodwork, panelling and kitchen cabinets. But you don't have to pay F&B money to get it on your walls.
The standout match is Dulux Summer Sage (LRV 28), which comes in at ΔE 2.1 from the original. Anything under 2.5 is what we'd call very close — you'd struggle to tell them apart on a finished wall, especially once the light shifts through the day. For a trade-priced paint with a wide range of finishes, that's a cracking result.
Running it a very close second is Crown Olive (LRV 27.1) at ΔE 2.2. The two are so near each other that your choice really comes down to which finish and sheen you prefer, and which you can get hold of locally. Crown's Easycare range is hard-wearing and wipeable, which is handy if this is going somewhere that takes knocks.
Worth a mention too is COAT's Jojo's Green (LRV 25.9), but be honest with yourself here — at ΔE 4.3 it's a noticeably different colour. It reads slightly different in undertone, so it's a green in the same family rather than a true dupe. If you specifically want Card Room Green, go Dulux or Crown.
One thing that genuinely matters: F&B's depth comes partly from its pigment load and the way it handles light, so colour-match dupes can look a touch flatter in dim, north-facing rooms. The fix is finish. Get your dupe mixed in a soft sheen — an eggshell on woodwork or a decent matt emulsion on walls — and the difference all but disappears.
Buy a tester of Summer Sage and Olive both, paint two big swatches on board, and live with them for a couple of days before you commit. Greens this complex shift more than most with the light.