Stone II from Paint & Paper Library's grey-green stone family — it's got a soft yellow-green underneath, which is exactly what makes it so easy to live with and exactly what'll trip you up if you treat it carelessly.
The golden rule: never put brilliant white next to it. Brilliant white will expose that yellow-green undertone and make the whole thing look grubby, like a wall that needs a wash. Instead, run your woodwork in a closely matched warm white — something soft and gentle that lets Stone II stay the star. Use it as a whole-room ground, walls and trim in the same family, and the room will feel calm and considered rather than chopped up.
For layering, work tonally rather than reaching for a contrast. Dulux Almost Pistachio (LRV 80.3) is a lovely lighter relation that picks up the green note and keeps things bright on a ceiling or in an adjoining space. Then go deeper in the soft furnishings — putty and stone tones, nothing too saturated.
When you do want a proper anchor, two directions work beautifully. Paint & Paper Library Blue Blood (LRV 16.4) gives you a deep, inky moment — gorgeous on a single piece of joinery or a study door, with enough depth to make Stone II glow against it. Or go earthy with Mylands Cigar BH.20 (LRV 11.8), a rich brown that flatters the warmth in the stone without fighting it.
The "but what about an accent colour?" question: resist it. Stone II doesn't want a bold pop. It wants warmth introduced through materials — antique brass fittings, limed oak, aged leather — rather than through paint. That's where it really sings.
Practical tip: sample your warm-white trim alongside Stone II in both morning and evening light before committing. The relationship between the two is the whole job here, and getting that match right is what separates a sophisticated scheme from a tired one.