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If the options are cherry, black pigmented walnut, or santos palisander (Bolivian rosewood), I would guess walnut.
One simple way the seller could prove it has faded, if indeed that is true, is to remove those 4 screws and show what it looks like where the light has not shone.
Here is where I found the wood choices. And I missed white pigmented walnut. https://www.vitra.com/en-gb/product/lounge-chair#t/tab-colors
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