I’m not sure how on/off trend saddle shoes are, but who cares. It’s about personal taste. If you like it, then wear them.
I think the white/navy saddles look great in the summer, especially with seersucker (either as a full suit or if you’re wearing the jacket and trousers separately with other elements).
I can see the dark brown/taupe looking good in the fall with denim, a tweed jacket (probably on the brown, cream end of things instead of the black/grey/white). They’d also look good with cords and moleskin trousers. In the warmer months, I think they’d look interesting with a casual suit, like a khaki chino suit.
Personally, I think they’d look a bit odd though with a navy suit or chinos — but I can’t put my finger on why.
ADDING thingsthatpleaseme replied:
By their nature, they’re bluchers which will look a bit off with a “city suite” like navy, anyhow. They’re definitely casual shoes, but I could see them being great with the right chinos. A suit would be a no go unless tweedy or something.