October Mist is one of those soft sage-greys that earns its keep by staying calm, so build the scheme around it accordingly. The single most important decision is your woodwork. Reach for a warm but not yellow white — something like a half-strength stone white — so the green registers properly instead of looking cold and clinical against a stark brilliant white.
Two off-whites do this beautifully. Paper III from Paint & Paper Library (LRV 75.3) is a creamy off-white that flatters October Mist without yellowing it, and Au Lait from Farrow & Ball (LRV 80) is even softer — a milky, barely-there warm white that lets the green do the talking on the walls. Either makes a lovely ceiling and trim partner.
For accents, go muted. Cigar BH.20 from Mylands (LRV 11.8) is a deep tobacco brown that grounds the scheme — gorgeous on a single piece of joinery, a fireplace surround, or in leather and timber. It reads as a natural earthy partner rather than a clash. If you want a touch more life, Fuchsia Falls 2 from Dulux (LRV 29.8) is a bright, cool magenta-pink that works in a cushion or a piece of art — sparingly, mind. Against a quiet sage-grey it's a proper flower-against-leaf jolt, and a little goes a long way.
The "but what about" question is always: can I add a brighter colour? Only in small, deliberate doses — that Fuchsia Falls cushion, not a wall. October Mist is a quiet neutral, and the moment you paint something saturated large — a clear teal, a strong yellow, a punchy navy — it stops looking deliberate and starts looking like an indecisive green. Keep the palette in the muted sage-to-charcoal family and let texture do the heavy lifting: linen, oak, brass, ceramics.
Practical tip: paint a big board in October Mist and stand it against your white, your darkest accent and your fabric before committing. In a north-facing room it'll lean greyer and cooler — that warm white trim becomes essential there.