tweed vest and different color tie.for mine maybe in the black or dark grey color scheme in cool prints. Why not have your Groomsmen wear the same vest/tuxedo, but all with different ties in the same color?
The groom looks distinct from his groomsmen. Here, the groom wears a suit jacket and traditional tie, while the guys don vests and bowties. I also like the idea of the grooms outfit being lighter or darker than his buddies
Image by Navy Blur - Bride in lace wedding dress & shoes with dried flower headpiece. Groom wears tweed suit & bow tie & bridesmaids in mis-match dresses for a rustic castle, vineyard & marquee wedding with autumnal colour scheme.
Groomsmen in jeans & vests. The guys are definitely on board! Match guys' shirt colors grey, tan vests, with boutonniere colors coordinated with respective bridesmaids' dress colors. All same vest. Groom: Different vest with white shirt.