If it's the dusky, brooding green-blue of Little Greene Livid you're after but you'd rather not pay Little Greene money, Dulux Midnight Garden is your best bet. It comes in at ΔE 2.9 from the original — that's very close, the kind of difference you'd only spot with the two swatches side by side under harsh light. With an LRV of 21 it carries roughly the same depth and weight on the wall, so it'll read as that same moody, characterful tone Livid is loved for.
The other two contenders are honest but not quite as faithful. Crown Fern Canopy (LRV 18.6) and COAT Adulting (LRV 16.2) both sit at ΔE 4 — close-ish, but you'd notice the shift. Fern Canopy leans a fraction greener and Adulting a touch deeper and more muted, so they're more "in the family" than dead-on dupes.
Now the bit everyone skips: paint quality isn't just colour. Little Greene's Intelligent Matt and Absolute Matt have a flatter, chalkier finish and a depth of pigment that budget trade emulsion doesn't always match. If you go Dulux, use their Heritage line rather than standard Diamond Matt where you can — the finish and pigment density are a lot closer to the premium feel. COAT, for what it's worth, punches well above its price on finish and is genuinely low-VOC, so Adulting is a solid shout if the slightly different tone suits you.
Practical advice: never buy on a ΔE figure alone. Order sample pots of Midnight Garden and Adulting, paint two coats on A2 lining paper, and live with them taped to the wall for a couple of days — north light in particular will pull a green like this around. Greens this deep also drink light, so they want a decent amount of it or a small room you're happy to make cosy. Get the match sorted on the wall, not on a chart, and you'll save proper money without regretting it.