Brown SCs are natural matches for grey and navy pants -- or tan/khaki for that matter, as long as the tones don't match too much. IMO brown-toned SCs are very versatile. The rusty tattersall looks perfect for that kind of thing. Also the navy isn't so dominant that you couldn't still wear with navy pants. It looks like a winner to me. Would definitely jump on that if I weren't already getting two Harris Tweed SCs.