Travertine is one of Little Greene's lovely warm stone neutrals — that soft, biscuity beige that sits beautifully in hallways and north-light rooms without going dull. If you're after the look for less, you've got a genuinely strong match available.
Dulux Bracken Salts 4 is the standout. At ΔE 0.8 from the original it's imperceptibly close — once it's on the wall and dry you'd never tell the two apart, and they share the same LRV of 61.8, so the light bounces back identically. This is as good as a dupe gets. If you're going to swap, this is the one.
If you'd prefer a different brand, COAT::Well Grounded comes in at ΔE 2.3, also LRV 61.8 — still a very close match and COAT's water-based formula is low-odour and quick to recoat, which makes it a doddle for a weekend job. Crown::Sandstone sits at ΔE 2.8 (LRV 60.6), which is a touch further off — close, but you may notice a hair more warmth or depth in certain lights. I'd only go for it if Crown's your preferred stockist.
The usual caveat: a tight ΔE tells you the colour is right, but it won't match Little Greene's finish character. Their Intelligent Matt and Absolute Matt have a particular chalky, deep look that a Dulux trade matt won't quite replicate. For most walls that difference is academic — but if you're matching into an existing Little Greene wall or chasing that specific velvety flatness, the original is worth the premium.
Practical advice: buy a tester of Bracken Salts 4 and paint two coats onto a bit of lining paper. Stand it against the wall morning and evening before you commit a whole room — warm neutrals like this shift more than you'd expect between daylight and lamplight. Get that right and you'll have Travertine's charm at a fraction of the cost.