Suit colour for a fall themed wedding?

The dresses are very pretty and i think light brown suits will match the bridesmaid

Navy is great for a fall colour scheme! My cousin and his groomsmen wore navy in his September wedding a few years ago.

I also think navy looks fantastic with orange-y rust shades

I honestly just google searched navy and rust color options and these came up

This is soooo pretty!

I am an autumn bride too and really like this colour combo. Do you remember where / at which site did you see this idea?

I think rust and navy will go great together! Here's some pictures that I've come across with that color theme

Your standard suit colours (grey, charcoal, navy) are pretty universal and won't clash with anything. They can be worn at all times of the year. Personally, and this would be my preference if I'm wearing navy in the fall as a groom, I would avoid a "rust/cinnamon" tie. First, it would feel like he's trying to match the bridesmaid dresses and if anything, he should be coordinating to match you! I would keep my ensemble fairly neutral: charcoal wool tie is sharp, dark enough of a shade for high formality without being depressing like black. Wool material also keeps it seasonal for the fall. Alternatively, pair it with one of your neutrals (Is it something along the lines of blush? That would go well with navy).

Finish the ensemble with a white pocket square (white being the most formal colour), and a pair of chestnut/walnut brown belt and shoes to finish the ensemble. You can also use a seasonal flower as the boutonniere to further reflect the season.

If your groomsmen are also wearing navy suits, they can incorporate the rust/cinnamon to match the bridesmaids via the pocket square. It's subtle and looks coordinated but won't look too overly matchy matchy with the bridesmaids. Just don't match it to the tie. Get a tie that works with the pocket square (patterned brown tie?) but not an exact match - that's a no no in menswear and comes off as looking too matchy matchy, as if dressed for prom.

The suit colour isn't usually included in the colour scheme. If anything, I'd avoid having suit colours be part of the decor so it doesn't overwhelm the outfit (imagine your fiancee wearing a navy suit sitting behind a table with navy table cloths).