^ I'm not a fan of khakis with tweed jackets either, though I get that they're a kind of US trad thing and that's consistent with the jacket & shirt style details . A trad look probably wouldn't have gone with a purple tie though, so that part doesn't quite mesh in the overall vibe. For me, though, the thing with chinos is not so much the colour but the fabric which looks more like a warmer weather material. I suppose you can get really heavy chinos, but still...
Wool trousers generally look good with tweed though, in a flannel or donegal weave for example. Cords almost always go great too. Colour-wise, pretty much any contrasting colour (e.g. a markedly different grey, dark green, chocolate brown, etc) will work . Sure, you could go wild with a different earthy shade too: mustard, orange, purple/plum, whatever... but you don't need to go there if it's not your bag. A dark blue also works for cords (in a similar way to how denim might work as a contrasting blue colour) but some folks in CM just don't like any dark blue non-suit trousers (for reasons I don't grok). If keeping the same top half, I think a very dark grey or dark plum would be great colours to use. If the tie was more navy blue than purple, that would open up the dark green or dark brown options more.
Other fabric options would include cavalry twill or moleskin, though I'm less a fan of these personally. Still, if one went for cavalry twill, khaki/light brown would be the typical/default colour, so it would be the smallest adjustment from shoreman's existing look while just changing the fabric to something heavier to echo the jacket fabric a bit more.
I still like the overall look of shore's outfit as is though.
