When looking for a fall wedding color think about what your favorite part of the fall is and use it as inspiration. Do you love the leaves from the trees? Then what about brown and red. Just think to your favorite thing about fall and use those colors.
Deep reds orange and purples. It would be great to work with the general colors of your region during that season and the time of day of the ceremony. Yellow is really questionable I think.
I love dark purple anytime of the year but I think it would look great with fall accent colors like browns and tans. You could use the fall colors in their bridal bouquets
I would suggest maybe orange, red, and brown. They are fall colors and you could easily get decorations from any store for them. Also you could maybe some straw or scarecrows at your wedding reception.