My favorite with brown field boots was a lovely lighter olive colored jacket. It had brown velvet trim on the collar too. I also used to wear light gray too. I would think a nice london-tan colored coat would look nice with those colored boots as well.
Do NOT wear a black jacket / Brown boots. Brown boots were/are for "cubbing" at which time one wears a nice tweed jacket... so I would get a light weight hunt jacket or a show jacket w/ a subtle pattern in it - something w/ browns/rust colors.
I love my brown field boots, and wear them proudly with rust breeches and a brown velvet helmet. I've worn them with light grey, dark grey and green coats and must say looked smashing every time out! I sometimes school in them with tan TS breeches, and that is a nice combo too.
OMG! can I wear my brown field boots in the hunter ring? It would look so much better with my hunter green coat and my liver chestnut horse. I wear them to ride everyday they are beautiful! I wear them in the show jumpers but didn't think they were acceptable in the hunter ring. I would be so happy if I could wear them! does anyone know? they wear the wild bedazzled and leather tri colored helmets!