We have featured one of these previously, but I'm flagging up this Robin Day 4-4000 armchair for Hille because of its unusual colour scheme and the cheap price.
The chair was made by Hille in the 1970s as part of a 'Living Theme' collection, which was pitched at a younger crowd and sold in cool places like Habitat. As you can, it's very much of its era.
Usually they're in cream (we have one in this colour), but the model on eBay is an unusual brown with contrast cord cushions (I think these are likely to be original too). An underrated space age gem and right now available for £99.