@Claghorn, thank you, I'll keep the formality issue in mind. It's just unfortunate that I very rarely favour black shoes over brown, regardless of the rules.
Would it be ok to wear this navy pin stripe suit with plainer brown shoes? cap toes?
If the suit were a solid navy, then full brogues would be alright?
I'd say yes on both counts. And that's a good way to think of balancing elements in clothing. You could move a bit here or move a bit there. Dark brown would have worked fine with that get up. Remove the stripes and maybe the vest, and brogued wingtips or captoes would work fine.
Something like this would've been perfect.