Edward Bulmer makes lovely paint — proper natural pigments, plant-based, genuinely breathable. But it's premium-priced, and if it's purely the *colour* of Ethereal Blue you're after, you've got two cracking alternatives that come in cheaper.
The best match is COAT::Hamilton at ΔE 2.4 from the original. Anything under 2.5 is what we'd call very close — you'd struggle to tell them apart on a wall. COAT is water-based, low-VOC, and sells direct so the pricing is sharp. Hamilton sits at LRV 48.1, so it bounces a fair bit of light around — a softly luminous mid-blue that'll feel calm rather than cold.
Close behind is Dulux::Highland Falls 3 at ΔE 2.6, with an LRV of 45.5. That's a hair more measured than the original, and Dulux availability means you can grab a tester from any decorator's merchant tomorrow. For the money, it's a sensible shout.
I'd steer you away from Crown::Curiosity here — at ΔE 5.4 and LRV 37.2 it's noticeably darker and reads as a different, deeper colour entirely. Not a match, even if it's in the same family.
Now, the honest caveat: a ΔE match gets you the colour, not the finish. Edward Bulmer's pigments give a particular chalky, light-absorbing depth that the cheaper acrylics won't replicate exactly, especially in low north-facing light. If Ethereal Blue is going on a feature wall you'll live with closely, order testers of both Hamilton and Highland Falls 3 and paint them up big — A4 minimum, two coats, viewed morning and evening.
If breathability and natural ingredients were the *reason* you wanted Edward Bulmer in the first place, don't swap — you'd be losing the point. But if it's just the blue you love, Hamilton gets you there for less.