Frosted Steel is a cool, steely grey with a faint blue undertone, and the trick is to commit to that coolness rather than fighting it. Try to warm it up with creamy whites and you'll get a muddy, indecisive result. Go cool and architectural instead — think metal, stone and clean light — and it sings.
For trim and ceilings, reach for a genuinely cool white. Farrow & Ball All White (LRV 92) is the one — no yellow, no grey, just a clean bright white that keeps Frosted Steel feeling fresh rather than gloomy. It's about as neutral as whites get, which is exactly what you want against a cool grey.
For depth and contrast, Paint & Paper Library Blue Blood (LRV 16.4) is a cracking partner. It's a dark inky blue that reads almost black in low light, perfect for a feature wall, joinery or the lower half of a panelled room. It anchors the scheme and makes the grey feel deliberate.
Now the bit that stops it going cold and clinical: a single warm accent. Mylands Beehive Place No.140 (LRV 58.6) brings a soft warm note in soft furnishings, a hallway or an adjoining nook — enough to add life without breaking the cool palette. And if you want real drama, Dulux Fuchsia Falls 2 (LRV 29.8) used sparingly — a door, a chair, artwork — gives that pop of colour cool greys love.
The "but what about" question is always lighting. Frosted Steel can tip flat and lifeless under warm 2700K bulbs. In a north-facing room especially, run daylight or neutral LEDs (around 4000K) so the cool tones stay crisp rather than dingy.
Practical advice: do this as a cool, modern scheme top to bottom — cool-white trim, one deep accent, one warm highlight. Sample all of it together on a board, view it morning and evening, and don't be tempted to soften the whites. The discipline is what makes it look designed.